Remove compressed (ETC1) texture support from Ganesh (take 2)

Reland of https://skia-review.googlesource.com/c/17456/ (Remove compressed (ETC1) texture support from Ganesh) but w/o removing third_part\etc1 files

TBR=bsalomon@google.com
Change-Id: I8ec4b7e3ddf47d213cb24c382731c050ffb8847f
Reviewed-on: https://skia-review.googlesource.com/17700
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/GrGpu.h b/src/gpu/GrGpu.h
index 259c573..897f2b8 100644
--- a/src/gpu/GrGpu.h
+++ b/src/gpu/GrGpu.h
@@ -100,8 +100,7 @@
      * @param budgeted    does this texture count against the resource cache budget?
      * @param texels      array of mipmap levels containing texel data to load.
      *                    Each level begins with full-size palette data for paletted textures.
-     *                    For compressed formats the level contains the compressed pixel data.
-     *                    Otherwise, it contains width*height texels. If there is only one
+     *                    It contains width*height texels. If there is only one
      *                    element and it contains nullptr fPixels, texture data is
      *                    uninitialized.
      * @return    The texture object if successful, otherwise nullptr.
@@ -546,13 +545,10 @@
 
     // overridden by backend-specific derived class to create objects.
     // Texture size and sample size will have already been validated in base class before
-    // onCreateTexture/CompressedTexture are called.
+    // onCreateTexture is called.
     virtual GrTexture* onCreateTexture(const GrSurfaceDesc& desc,
                                        SkBudgeted budgeted,
                                        const SkTArray<GrMipLevel>& texels) = 0;
-    virtual GrTexture* onCreateCompressedTexture(const GrSurfaceDesc& desc,
-                                                 SkBudgeted budgeted,
-                                                 const SkTArray<GrMipLevel>& texels) = 0;
 
     virtual sk_sp<GrTexture> onWrapBackendTexture(const GrBackendTexture&,
                                                   GrSurfaceOrigin,