RELEASE_NOTES.txt

Skia Graphics Release Notes

This file includes a list of high level updates for each milestone release.

* * *

Milestone 88
------------
  * <insert new release notes here>

  * New variant of SkImage::MakeFromYUVATextures. Takes a new type GrYUVATextures
    which wraps an SkYUVAInfo and compatible set of GrBackendTextures. The provides
    a more complete and structured specification of the planar configuration. Previous
    version is deprecated.

  * SkTPin() removed from public API.

  * Add new SkImageFilters::Blend factory function, in place of the now deprecated
    SkImageFilters::Xfermode factory function. Behavior is identical, but name better matches
    conventions in SkShader and SkColorFilter.
    https://review.skia.org/324623

  * SkImageFilters::Foo() factory functions now accept SkIRect, SkRect, and optional SkIRect* or
    SkRect*, instead of previously just the optional SkIRect*. Internally, the crop rects are stored
    as floats to allow for fractional crops to be defined in the local coordinate system (before
    transformation by the canvas matrix).
    https://review.skia.org/324622

  * Add new SkImageFilters::Shader factory and deprecate SkImageFilters::Paint factory. All
    supported/valid Paint() filters can be represented more cleanly as a Shader image filter.
    https://review.skia.org/323680

  * GrContext has been replaced by two separate classes: GrDirectContext which is
    the traditional notion of GrContext, and GrRecordingContext which is a context
    that is recording an SkDeferredDisplayList and therefore has reduced functionality.
    Unless you are using SkDeferredDisplayList, migrate directly to GrDirectContext in
    all cases.

  * CPU sync bool added to SkSurface::flushAndSubmit() and GrContext::flushAndSubmit()

  * Removed legacy variant of SkImage::MakeFromYUVAPixmaps. Use the version that
    takes SkYUVAPixmaps instead. It has a more structured description of the
    planar configuration.
    https://review.skia.org/322480

  * Some SkImage YUV image factories have been removed. Replacement patterns
    outlined below.
    SkImage::MakeFromYUVATexturesCopy
        1) Make SkImage from YUVA planes using SkImage::MakeFromYUVATextures
        2) Use Skia to allocate a surface using SkSurface::MakeRenderTarget
        3) surface->getCanvas()->drawImage(image, 0, 0);
        4) surface->makeImageSnapShot() produces RGBA image.
    SkImage::MakeFromYUVATexturesCopyWithExternalBackend
        1) Make image using MakeFromYUVATextures
        2) Make a SkSurface around result texture using SkSurface::MakeFromBackendTexture
        3) surface->getCanvas()->drawImage(image, 0, 0);
        4) surface->flushAndSubmit()
        5) Optional: SkImage::MakeFromBackendTexture() to use as SkImage.
    SkImage::MakeFromNV12TexturesCopy
        Same as SkImage::MakeFromYUVATexturesCopy
    https://review.skia.org/321537

  * GrBackendRenderTargets which are created with a stencilBits param, now require
    the stencilBits to be 0, 8, or 16.
    https://review.skia.org/321545

* * *

Milestone 87
------------

  * GrVkImageInfo now has a field for sample count. GrBackendRenderTarget constructor
    that took both a GrVkImageInfo and separate sample count is deprecated. Use the
    version without sample count instead. Similarly, GrD3DTextureResourceInfo now
    has a sample count field and GrBackendRenderTarget no longer takes a separate
    sample count for Direct3D. The sample count for GrBackendRenderTarget is now
    directly queried from MtlTexture rather than passed separately. The version that
    takes a separate sample count is deprecated and the parameter is ignored.
    https://review.skia.org/320262
    https://review.skia.org/320757
    https://review.skia.org/320956

  * Added deprecation warning for Metal support on MacOS 10.13, iOS 8.3, and older.
    https://review.skia.org/320260

  * GrVkImageInfo now has a field for sample count. GrBackendRenderTarget constructor
    that took both a GrVkImageInfo and separate sample count is deprecated. Use the
    version without sample count instead.

  * Update SkClipOp::kMax_EnumValue to include only intersect and difference when
    SK_SUPPORT_DEPRECATED_CLIPOPS is not defined.
    https://review.skia.org/320064

  * Add support for external allocator for Direct3D 12 backend.
    Defines base classes for an allocation associated with a backend texture and a
    a memory allocator to create such allocations.
    Adds memory allocator to backend context.
    https://review.skia.org/317243

  * Add new optional parameter to GrContext::setBackend[Texture/RenderTarget]State which can
    be used to return the previous GrBackendSurfaceMutableState before the requested change.
    https://review.skia.org/318698

  * New optimized clip stack for GPU backends. Enabled by default but old behavior based on
    SkClipStack can be restored by defining SK_DISABLE_NEW_GR_CLIP_STACK when building. It is not
    compatible with SK_SUPPORT_DEPRECATED_CLIPOPS and we are targeting the removal of support for
    the deprecated, expanding clip ops.
    https://review.skia.org/317209

  * GPU backends now properly honor the SkFilterQuality when calling drawAtlas.
    https://review.skia.org/313081

  * The signature of 'main' used with SkRuntimeEffect SkSL has changed. There is no longer an
    'inout half4 color' parameter, effects must return their color instead.
    Valid signatures are now 'half4 main()' or 'half4 main(float2 coord)'.
    https://review.skia.org/310756

  * New YUVA planar specifications for SkCodec, SkImageGenerator, SkImage::MakeFromYUVAPixmaps.
    Chroma subsampling is specified in more structured way. SkCodec and SkImageGenerator
    don't assume 3 planes with 8bit planar values. Old APIs are deprecated.
    https://review.skia.org/309658
    https://review.skia.org/312886
    https://review.skia.org/314276
    https://review.skia.org/316837
    https://review.skia.org/317097

  * Added VkImageUsageFlags to GrVkImageInfo struct.

* * *

Milestone 86
------------

  * Remove support for 'in' variables from SkRuntimeEffect. API now exclusively refers to inputs
    as 'uniforms'.
    https://review.skia.org/309050

  * Add SkImageGeneratorNDK and SkEncodeImageWithNDK for using Android's NDK APIs to decode and
    encode.
    https://review.skia.org/308185
    https://review.skia.org/308800

  * SkImage:remove DecodeToRaster, DecodeToTexture
    https://review.skia.org/306331

  * Add GrContext api to update compressed backend textures.
    https://review.skia.org/302265

  * Rename GrMipMapped to GrMipmapped for consistency with new APIs.
    Also rename GrBackendTexture::hasMipMaps() to GrBackendTexture::hasMipmaps()
    https://review.skia.org/304576
    https://review.skia.org/304598

  * Add option for clients to own semaphores after wait calls.
    https://review.skia.org/301216

  * Remove obsolete GrFlushFlags.
    https://review.skia.org/298818

  * Adds default flush() calls to SkSurface, SkImage, and GrContext. These calls do
    a basic flush without a submit. If you haven't updated Skia in a couple releases
    and still have flush() calls in your code that you expect to do a flush and
    submit, you should update all those to the previously added flushAndSubmit() calls
    instead.
    https://review.skia.org/299141

  * Enable BackendSemaphores for the Direct3D backend.
    https://review.skia.org/298752

  * Added SkImage:asyncRescaleAndReadPixels and SkImage::asyncRescaleAndReadPixelsYUV420
    https://review.skia.org/299281

  * Ganesh is moving towards replacing GrContext with the GrDirectContext/GrRecordingContext
    pair. GrDirectContexts have _direct_ access to the GPU and are very similar to the old
    GrContext. GrRecordingContexts are less powerful contexts that lack GPU access but provided
    context-like utilities during DDL recording. SkSurfaces and SkCanvas will now only return
    GrRecordingContexts. Clients requiring context features that need GPU access can then
    check (via GrRecordingContext::asDirectContext) if the available recording context is actually
    a direct context.

  * Replace #defined values in SkString with equivalent constexprs.
    http://review.skia.org/306160

* * *

Milestone 85
------------

  * Added GrContext::oomed() which reports whether Skia has seen a GL_OUT_OF_MEMORY
    error from Open GL [ES] or VK_ERROR_OUT_OF_*_MEMORY from Vulkan.
    https://review.skia.org/298216

  * Add option on SkSurface::flush to pass in a GrBackendSurfaceMutableState which
    we will set the gpu backend surface to be at the end of the flush.
    https://review.skia.org/295567

  * Add GrContext function to set mutable state on a backend surface. Currently this
    is only used for setting vulkan VkImage layout and queue family.
    https://review.skia.org/293844

  * SkSurface factores that take GrBackendTexture or GrBackendRenderTarget now always
    call the release proc (if provided) on failure. SkSurface::replaceBackendTexture
    also calls the release proc on failure.
    https://review.skia.org/293762

  * SkSurface::asyncRescaleAndReadPixels and SkSurfaceasyncRescaleAndReadPixelsYUV420
    now require explicit GrContext submit to guarantee finite time before callback
    is invoked.
    https://review.skia.org/292840

  * Add VkSharingMode field to GrVkImageInfo.
    https://review.skia.org/293559

  * Move SkBitmapRegionDecoder into client_utils/android.

  * SkCanvas.clear and SkCanvas.drawColor now accept SkColor4f in addition to SkColor.

  * Remove SkSurface::MakeFromBackendTextureAsRenderTarget.
    This factory existed to work around issues with GL_TEXTURE_RECTANGLE that existed
    in Chrome's command buffer. Those issues have since been resolved. Use
    SkSurface::MakeFromBackendTexutre or SkSurface::MakeFromBackendRenderTarget instead.
    https://review.skia.org/292719

  * Adds submittedProc callback to GrFlushInfo which will be called when the work
    from the flush call is submitted to the GPU. This is specifically useful for knowing
    when semahpores sent with the flush have been submitted and can be waiting on.
    https://review.skia.org/291078

  * GrContext submit is now required to be called in order to send GPU work to the
    actual GPU. The flush calls simply produces 3D API specific objects that are ready
    to be submitted (e.g. command buffers). For the GL backend, the flush will still
    send commands to the driver. However, clients should still assume the must call
    submit which is where any glFlush that is need for sync objects will be called. There,
    are flushAndSubmit() functions of GrContext, SkSurface, and SkImage that will act
    like the previous flush() functions. This will flush the work and immediately call
    submit.
    https://review.skia.org/289033

  * Remove deprecated version of flush calls on GrContext and SkSurface.
    https://review.skia.org/2290540

  * SkCanvas::drawVertices and drawPatch now support mapping an SkShader without explicit
    texture coordinates. If they're not supplied, the local positions (vertex position or
    patch cubic positions) will be directly used to sample the SkShader.
    https://review.skia.org/290130

* * *

Milestone 84
------------

  * Add api on GrContext, updateBackendTexture that will upload new data to a
    GrBackendTexture.
    https://review.skia.org/288909

  * Add GrContext getter to SkSurface.
    https://review.skia.org/289479

  * Deprecate GrContext and SkSurface flush() call and replace ith with flushAndSubmit().
    This only effects the default flush call that takes no parameters.
    https://review.skia.org/289478

  * GrContext::createBackendTexture functions that initialize the texture no longer
    guarantee that all the data has been uploaded and the gpu is done with the texture.
    Instead the client can assume the upload work has been submitted to the gpu and they
    must wait for that work to finish before deleting the texture. This can be done via
    their own synchronization or by passing in a finish proc into the create calls which
    will be called when it is safe to delete the texture (at least in terms of work
    done during the create).
    https://review.skia.org/286517

  * Remove unused SkMaskFilter helpers: compbine, compose
    Note: shadermaskfilter will likely be removed next (clipShader should serve)

  * Add back SkCanvas::kPreserveLCDText_SaveLayerFlag to indicate that saveLayer()
    will preserve LCD-text. All text in the layer must be drawn on opaque background
    to ensure correct rendering.

  * Add the new directory client_utils/ for code that is specific to a single client and
    should be considered separate from Skia proper. Move SkFrontBufferedStream into the
    subdir android/.

  * SkBitmap and SkPixmap's erase() methods now treat their color parameters
    consistently with the rest of Skia, with all SkColors and any untagged
    SkColor4fs interpreted as sRGB, not as a color in the bitmap's color space.
    SkPixmap::erase(SkColor4f) now takes an SkColorSpace, so you can pass
    pixmap.colorSpace() if you want the old behavior.

  * SkCamera.h and SkMatrix44.h are DEPRECATED.
    Use SkM44 if you want to have 3d transformations.

  * Changed Dilate and Erode image filters to take SkScalar for radius instead of int. While
    the image filters themselves are defined in terms of discrete pixels, the radii provided by
    the user are mapped through the CTM so taking ints forced over discretization. After mapping
    through the CTM the radii are now rounded to pixels.
    https://review.skia.org/281731
    https://review.skia.org/282636

  * Updated the contract of GrContext and SkSurface flush calls in regards to semaphores. Made it
    clear that the caller is responsible for deleting any initialized semaphores after the flush
    call regardless if we were able to submit them or not. Also, allows skia to only submit a
    subset of the requested semaphores if we failed to create some.
    https://review.skia.org/282265


  * SkCanvas::drawVertices will now always fill the triangles specified by the vertices. Previously,
    vertices with no colors and no (texture coordinates or shader) would be drawn in wireframe.
    https://review.skia.org/282043

* * *

Milestone 83
------------

  * Remove localmatrix option from SkShaders::[Blend, Lerp]

  * Fill out Direct3D parameters for backend textures and backend rendertargets.

  * SkImage::makeTextureImage() takes an optional SkBudgeted param

  * Made non-GL builds of GPU backend more robust.
    https://review.skia.org/277456

  * MoltenVK support removed. Use Metal backend instead.
    https://review.skia.org/277612

* * *

Milestone 82
------------

  * Removed drawBitmap and related functions from SkDevice; all public drawBitmap functions on
    SkCanvas automatically wrap the bitmap in an SkImage and call the equivalent drawImage function.
    Drawing mutable SkBitmaps will now incur a mandatory copy. Switch to using SkImage directly or
    mark the bitmap as immutable before drawing.

  * Removed "volatile" flag from SkVertices. All SkVertices objects are assumed to be
    volatile (the previous default behavior).

  * Removed exotic legacy bitmap functions from SkCanvas (drawBitmapLattic, drawBitmapNine); the
    exotic SkImage functions still exist.

  * Make it possible to selectively turn on/off individual encoders/decoders,
    using skia_use_(libpng/libjpeg_turbo/libwebp)(decode/encode).

  * Removed GrGpuResource, GrSurface, and GrTexture from public api. These were not
    meant to be public, and we now can move them into src. Also removed getTexture
    function from SkImage.h

  * Removed Bones from SkVertices

  * Added a field to GrContextOptions that controls whether GL errors are checked after
    GL calls that allocate textures, etc. It also controls checking for shader compile
    success, and program linking success.

  * Made SkDeferredDisplayList.h officially part of the public API (i.e., moved it to
    include/core). Also added a ProgramIterator to SkDeferredDisplayList which allows
    clients to pre-compile some of the shaders the DDL requires.

  * Added two new helper methods to SkSurfaceCharacterization: createBackendFormat and
    createFBO0. These make it easier for clients to create new surface characterizations that
    differ only a little from an existing surface characterization.

  * Removed SkTMax and SkTMin.
  * Removed SkTClamp and SkClampMax.
  * Removed SkScalarClampMax and SkScalarPin.
  * Removed SkMax32 and SkMin32.
  * Removed SkMaxScalar and SkMinScalar.

  * SkColorSetA now warns if the result is unused.

  * An SkImageInfo with a null SkColorSpace passed to SkCodec::getPixels() and
    related calls is treated as a request to do no color correction at decode
    time.

  * Add new APIs to add attributes to document structure node when
    creating a tagged PDF.

  * Remove CGFontRef parameter from SkCreateTypefaceFromCTFont.
    Use CTFontManagerCreateFontDescriptorFromData instead of
    CGFontCreateWithDataProvider to create CTFonts to avoid memory use issues.

  * Added SkCodec:: and SkAndroidCodec::getICCProfile for reporting the native
    ICC profile of an encoded image, even if it doesn't map to an SkColorSpace.

  * SkSurface::ReplaceBackendTexture takes ContentChangeMode as a parameter,
    which allow callers to specify whether retain a copy of the current content.

  * Enforce the existing documentation in SkCanvas::saveLayer that it ignores
    any mask filter on the restore SkPaint. The 'coverage' of a layer is
    ill-defined, and masking should be handled by pre-clipping or using the
    auxiliary clip mask image of the SaveLayerRec.

* * *

Milestone 81
------------

  * Added support for GL_NV_fence extension.

  * Make SkImageInfo::validRowBytes require rowBytes to be pixel aligned. This
    makes SkBitmap match the behavior of raster SkSurfaces in rejecting
    non-aligned rowBytes.

  * Added an SkImage::MakeRasterFromCompressed entry point. Also updated
    SkImage::MakeFromCompressed to decompress the compressed image data if
    the GPU doesn't support the specified compression type (i.e., macOS Metal
    doesn't support BC1_RGB8_UNORM so such compressed images will always be
    decompressed on that platform).

  * Added support for BC1 RGBA compressed textures

  * Added CachingHint to SkImage::makeRasterImage

  * Added SkAnimatedImage::getCurrentFrame()

  * Add support to create an SkSurface from an MTKView, with delayed acquisition of
    the MTLDrawable.
    Entry point: SkSurface::MakeFromMTKView

  * Removed SkIRect::EmptyIRect(). Use SkIRect::MakeEmpty() instead.
    https://review.skia.org/262382/

  * Moved SkRuntimeEffect to public API. This is the new (experimental) interface to custom SkSL
    shaders and color filters.

  * Added BC1 compressed format support. Metal and Vulkan seem to only support the BC
    formats on desktop machines.

  * Added compressed format support for backend texture creation API.
    This adds the following new entry points:
    GrContext::compressedBackendFormat
    GrContext::createCompressedBackendTexture
    The latter method comes in variants that allow color-initialized and
    compressed texture data initialized.

  * Added SkMatrix::MakeTrans(SkIVector)
    https://review.skia.org/259804

* * *

Milestone 80
------------

  * For Vulkan backend, we now require that the VkDevice, Queue, and Instance outlive
    either the destruction or abandoning of the GrContext. Additionally, all
    GrBackendTextures created via GrContext::createBackendTexture calls must be deleted
    before destroying or abandoning the GrContext.
    https://review.skia.org/257921

  * Removed SkSize& SkSize::operator=(const SkISize&)
    https://review.skia.org/257880

  * SkISize width() and height() now constexpr
    https://review.skia.org/257680

  * Added SkMatrix::MakeTrans(SkVector) and SkRect::makeOffset(SkVector).
    https://review.skia.org/255782

  * Added SkImageInfo::MakeA8(SkISize) and added optional color space parameter to
    SkImageInfo::MakeN32Premul(SkISize).

  * Added dimensions() and getFrameCount() to SkAnimatedImage
    https://review.skia.org/253542

  * Removed SkMatrix44 version of toXYZD50 from SkColorSpace. Switched to skcms types in
    transferFn, invTrasnferFn, and gamutTransformTo functions.
    https://review.skia.org/252596

  * Removed rotation and YUV support from SkColorMatrix
    https://review.skia.org/252188

  * Added kBT2020_SkYUVColorSpace. This is BT.2020's YCbCr conversion (non-constant-luminance).
    https://review.skia.org/252160

  * Remove old async read pixels APIs
    https://review.skia.org/251198

  * Expose SkBlendModeCoeff and SkBlendMode_AsCoeff for Porter-Duff blend modes.
    https://review.skia.org/252600

* * *

Milestone 79
------------

  * SkTextBlob::Iter to discover the glyph indices and typefaces in each run
    https://skia-review.googlesource.com/246296

  * Added support for PQ and HLG transfer functions to SkColorSpace.
    https://skia-review.googlesource.com/c/skia/+/249000

  * Added new api on GrContext ComputeImageSize. This replaces the hold static helper
    ComputeTextureSize.
    https://skia-review.googlesource.com/c/skia/+/247337

  * New versions of SkSurface async-rescale-and read APIs that allow client to extend
    the lifetime of the result data. Old versions are deprecated.
    https://review.skia.org/245457

  * Add SkColorInfo. It's dimensionless SkImageInfo.
    https://review.skia.org/245261

  * Added SkPixmap-based createBackendTexture method to GrContext. This allows clients to create
    backend resources (initialized with texture data) that Skia/Ganesh doesn't know about/track.
    https://review.skia.org/244676

  * Add explicit src and dst colorspace parameters to SkColorFilter::filterColor4f()
    https://review.skia.org/244882

  * Remove Vulkan/Metal float32 RGBA texture support
    https://review.skia.org/244881

  * Add SkSurface::MakeFromCAMetalLayer
    https://review.skia.org/242563

  * Added kAlpha_F16_SkColorType, kRG_F16_SkColorType and kRGBA_16161616_SkColorType.
    This is intended to help support HDR YUV uses case (e.g., P010 and P016). As such,
    the addition is focused on allowing creation of SkPixmaps and SkImages and not
    SkSurfaces (i.e., who wants to render to render to these?)
    https://review.skia.org/241357

  * Start to move nested SkPath types (e.g. Direction, Verb) up to root level in SkPathTypes.h
    https://review.skia.org/241079

  * Remove isRectContour and ksNestedFillRects from public
    https://review.skia.org/241078

  * Added kRG_88_SkColorType. This is intended to help support YUV uses case (e.g., NV12).
    As such, the addition is focused on allowing creation of SkPixmaps and SkImages and not
    SkSurfaces (i.e., who wants to render to RG?)
    https://review.skia.org/239930
    https://review.skia.org/235797

  * Make the size of program/pipeline caches configurable via
    GrContextOptions::fRuntimeProgramCacheSize
    https://review.skia.org/239756

  * Added kAlpha_16_SkColorType and kRG_1616_SkColorType. This is intended to help support HDR YUV
    uses case (e.g., P010 and P016). As such, the addition is focused on allowing creation of
    SkPixmaps and SkImages and not SkSurfaces (i.e., who wants to render to render to these?)
    https://review.skia.org/239930

  * Add GrContext::precompileShader to allow up-front compilation of previously-cached shaders.
    https://review.skia.org/239438

* * *

Milestone 78
------------

  * SkDrawLooper is no longer supported in SkPaint or SkCanvas.
    https://review.skia.org/230579
    https://review.skia.org/231736

  * SkPath::Iter::next() now ignores its consumDegenerates bools. Those will so
    go away entirely
    https://review.skia.org/235104

  * SkImage: new factories: DecodeToRaster, DecodeToTexture
    https://review.skia.org/234476

  * SkImageFilter API refactor started:
    - Provide new factory API in include/effects/SkImageFilters
    - Consolidated enum types to use SkTileMode and SkColorChannel
    - Hide filter implementation classes
    - Hide previously public functions on SkImageFilter that were intended for
      internal use only
    https://review.skia.org/230198
    https://review.skia.org/230876
    https://review.skia.org/231256

  * SkColorFilters::HSLAMatrix - new matrix color filter operating in HSLA
    space.
    https://review.skia.org/231736

  * Modify GrBackendFormat getters to not return internal pointers. Use an enum
    class for GL formats.
    https://review.skia.org/233160

  * Expose GrContext::dump() when SK_ENABLE_DUMP_GPU is defined.
    https://review.skia.org/233557

  * Vulkan backend now supports YCbCr sampler for I420 Vulkan images that are
    not backed by external images.
    https://review.skia.org/233776

  * Add SkCodec::SelectionPolicy for distinguishing between decoding a still
    image or an image sequence for a container format that has both (e.g. HEIF).
    https://review.skia.org/232839

  * SkImage::makeTextureImage and SkImage::MakeCrossContextFromPixmap no longer
    take an SkColorSpace parameter. It was unused.
    https://review.skia.org/234579
    https://review.skia.org/234912

  * SkImage::reinterpretColorSpace - to reinterpret image contents in a new
    color space.
    https://review.skia.org/234328

  * Removed SkImage::MakeCrossContextFromEncoded.
    https://review.skia.org/234912

  * Add Metal support for GrFence, GrSemaphore, and GrBackendSemaphore
    https://review.skia.org/233416

  * SkMallocPixelRef: remove MakeDirect and MakeWithProc from API.
    https://review.skia.org/234660

  * Remove 4-parameter variant of SkRect::join() and intersect(), and
    noemptycheck variants of intersect().
    https://review.skia.org/235832
    https://review.skia.org/237142

  * Remove unused sk_sp comparison operators.
    https://review.skia.org/236942

  * Add SkColor4f variant to experimental_DrawEdgeAAQuad for SkiaRenderer.
    https://review.skia.org/237492

  * Deprecated maxCount resource cache limit for Ganesh.
    This hasn't been relevant for a long time.

  * Changed GrContextOptions' fDisallowGLSLBinaryCaching to fShaderCacheStrategy,
    and allow caching SkSL.
    https://review.skia.org/238856

  * Use GL_QCOM_TILED_RENDERING to explicitly discard stencil

  * Added RELEASE_NOTES.txt file
    https://review.skia.org/229760

  * Implemented internal support for OpenGL tessellation.