Revert of Hide SkCanvas::LayerIter (patchset #2 id:20001 of https://codereview.chromium.org/1897863008/ )

Reason for revert:
Das roll ist gebusted: https://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_ng/builds/214775/steps/compile%20%28with%20patch%29/logs/stdio

FAILED: /b/build/slave/cache/cipd/goma/gomacc ../../third_party/llvm-build/Release+Asserts/bin/clang++ -MMD -MF obj/third_party/WebKit/Source/platform/graphics/paint/blink_platform_unittests.PaintArtifactToSkCanvasTest.o.d -DV8_DEPRECATION_WARNINGS -DCLD_VERSION=2 -D__ASSERT_MACROS_DEFINE_VERSIONS_WITHOUT_UNDERSCORE=0 -DCHROMIUM_BUILD -DCR_CLANG_REVISION=266460-1 -DUSE_LIBJPEG_TURBO=1 -DENABLE_WEBRTC=1 -DENABLE_MEDIA_ROUTER=1 -DUSE_PROPRIETARY_CODECS -DENABLE_PEPPER_CDMS -DENABLE_NOTIFICATIONS -DENABLE_TOPCHROME_MD=1 -DDCHECK_ALWAYS_ON=1 -DFIELDTRIAL_TESTING_ENABLED -DENABLE_TASK_MANAGER=1 -DENABLE_EXTENSIONS=1 -DENABLE_PDF=1 -DENABLE_PLUGIN_INSTALLATION=1 -DENABLE_PLUGINS=1 -DENABLE_SESSION_SERVICE=1 -DENABLE_THEMES=1 -DENABLE_AUTOFILL_DIALOG=1 -DENABLE_PRINTING=1 -DENABLE_BASIC_PRINTING=1 -DENABLE_PRINT_PREVIEW=1 -DENABLE_SPELLCHECK=1 -DUSE_BROWSER_SPELLCHECKER=1 -DENABLE_CAPTIVE_PORTAL_DETECTION=1 -DENABLE_APP_LIST=1 -DENABLE_SETTINGS_APP=1 -DENABLE_SUPERVISED_USERS=1 -DENABLE_SERVICE_DISCOVERY=1 -DV8_USE_EXTERNAL_STARTUP_DATA -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DINSIDE_BLINK -DMOJO_USE_SYSTEM_IMPL -DGTEST_HAS_POSIX_RE=0 -DGTEST_LANG_CXX11=0 -DUNIT_TEST -DGTEST_HAS_RTTI=0 -DENABLE_LAYOUT_UNIT_IN_INLINE_BOXES=0 -DENABLE_OILPAN=1 -DWTF_USE_CONCATENATED_IMPULSE_RESPONSES=1 -DENABLE_INPUT_MULTIPLE_FIELDS_UI=1 -DWTF_USE_ICCJPEG=1 -DWTF_USE_QCMSLIB=1 -DU_USING_ICU_NAMESPACE=0 -DU_ENABLE_DYLOAD=0 -DU_NOEXCEPT= -DU_STATIC_IMPLEMENTATION -DSK_SUPPORT_GPU=1 -DSK_IGNORE_LINEONLY_AA_CONVEX_PATH_OPTS -DCHROME_PNG_WRITE_SUPPORT -DPNG_USER_CONFIG -DUSE_LIBPCI=1 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -D_FORTIFY_SOURCE=2 -Igen -Igen/blink -I../.. -I../../skia/config -I../../third_party/WebKit/Source -I../../third_party/khronos -I../../gpu -Igen/angle -I../../third_party/WebKit -Igen/third_party/WebKit -I../../testing/gmock/include -I../../testing/gtest/include -I../../third_party/icu/source/i18n -I../../third_party/icu/source/common -I../../third_party/skia/include/core -I../../third_party/skia/include/effects -I../../third_party/skia/include/pdf -I../../third_party/skia/include/gpu -I../../third_party/skia/include/lazy -I../../third_party/skia/include/pathops -I../../third_party/skia/include/pipe -I../../third_party/skia/include/ports -I../../third_party/skia/include/utils -I../../third_party/skia/include/utils/mac -I../../skia/ext -I../../third_party/harfbuzz-ng/src -I../../third_party/qcms/src -I../../third_party/libpng -I../../third_party/zlib -I../../third_party/libwebp -I../../third_party/ots/include -I../../v8/include -I../../third_party/iccjpeg -I../../third_party/libjpeg_turbo -isysroot /Applications/Xcode5.1.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk -O2 -fvisibility=hidden -Werror -mmacosx-version-min=10.7 -arch x86_64 -Wall -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wno-selector-type-mismatch -Wpartial-availability -Wheader-hygiene -Wno-char-subscripts -Wno-unneeded-internal-declaration -Wno-covered-switch-default -Wstring-conversion -Wno-c++11-narrowing -Wno-deprecated-register -Wno-inconsistent-missing-override -Wno-shift-negative-value -std=c++11 -stdlib=libc++ -fno-rtti -fno-exceptions -fvisibility-inlines-hidden -fno-threadsafe-statics -Xclang -load -Xclang /b/build/slave/mac/build/src/third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.dylib -Xclang -add-plugin -Xclang find-bad-constructs -Xclang -plugin-arg-find-bad-constructs -Xclang check-templates -Xclang -plugin-arg-find-bad-constructs -Xclang follow-macro-expansion -Xclang -plugin-arg-find-bad-constructs -Xclang check-implicit-copy-ctors -fcolor-diagnostics -fno-strict-aliasing -Xclang -load -Xclang /b/build/slave/mac/build/src/third_party/llvm-build/Release+Asserts/lib/libBlinkGCPlugin.dylib -Xclang -add-plugin -Xclang blink-gc-plugin -Xclang -plugin-arg-blink-gc-plugin -Xclang enable-oilpan -Xclang -plugin-arg-blink-gc-plugin -Xclang warn-raw-ptr  -c ../../third_party/WebKit/Source/platform/graphics/paint/PaintArtifactToSkCanvasTest.cpp -o obj/third_party/WebKit/Source/platform/graphics/paint/blink_platform_unittests.PaintArtifactToSkCanvasTest.o
../../third_party/WebKit/Source/platform/graphics/paint/PaintArtifactToSkCanvasTest.cpp:201:22: error: 'LayerIter' is a protected member of 'SkCanvas'
    return SkCanvas::LayerIter(canvas, false).clip();
                     ^
../../third_party/skia/include/core/SkCanvas.h:1230:18: note: declared protected here
    class SK_API LayerIter /*: SkNoncopyable*/ {
                 ^
1 error generated.
ninja: build stopped: subcommand failed.

Original issue's description:
> Hide SkCanvas::LayerIter
>
> GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1897863008
>
> Committed: https://skia.googlesource.com/skia/+/a814000cbb0e90624a410b4359fff7f3ec66f0e0

TBR=reed@google.com,robertphillips@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1906573003
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index e7b7571..70c3663 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -1220,7 +1220,6 @@
 
     ///////////////////////////////////////////////////////////////////////////
 
-protected:
     /** After calling saveLayer(), there can be any number of devices that make
         up the top-most drawing area. LayerIter can be used to iterate through
         those devices. Note that the iterator is only valid until the next API
@@ -1259,7 +1258,6 @@
         bool              fDone;
     };
 
- public:
     // don't call
     GrRenderTarget* internal_private_accessTopLayerRenderTarget();
 
@@ -1434,7 +1432,6 @@
     void checkForDeferredSave();
     void internalSetMatrix(const SkMatrix&);
 
-    friend class CanvasTestingAccess; // for testing
     friend class SkDrawIter;        // needs setupDrawForLayerDevice()
     friend class AutoDrawLooper;
     friend class SkLua;             // needs top layer size and offset
diff --git a/samplecode/SampleLayers.cpp b/samplecode/SampleLayers.cpp
index 4386976..194f0a7 100644
--- a/samplecode/SampleLayers.cpp
+++ b/samplecode/SampleLayers.cpp
@@ -12,6 +12,7 @@
 #include "SkCamera.h"
 #include "SkColorFilter.h"
 #include "SkColorPriv.h"
+#include "SkDevice.h"
 #include "SkGradientShader.h"
 #include "SkImage.h"
 #include "SkInterpolator.h"
@@ -34,6 +35,22 @@
     paint->setXfermodeMode(SkXfermode::kDstIn_Mode);
 }
 
+static void dump_layers(const char label[], SkCanvas* canvas) {
+    SkDebugf("Dump Layers(%s)\n", label);
+
+    SkCanvas::LayerIter iter(canvas, true);
+    int index = 0;
+    while (!iter.done()) {
+        SkImageInfo info = iter.device()->imageInfo();
+        const SkIRect& clip = iter.clip().getBounds();
+        SkDebugf("Layer[%d] bitmap [%d %d] X=%d Y=%d clip=[%d %d %d %d] alpha=%d\n", index++,
+                 info.width(), info.height(), iter.x(), iter.y(),
+                 clip.fLeft, clip.fTop, clip.fRight, clip.fBottom,
+                 iter.paint().getAlpha());
+        iter.next();
+    }
+}
+
 // test drawing with strips of fading gradient above and below
 static void test_fade(SkCanvas* canvas) {
     SkAutoCanvasRestore ar(canvas, true);
@@ -69,6 +86,8 @@
         p.setAntiAlias(true);
         canvas->drawOval(r, p);
 
+        dump_layers("inside layer alpha", canvas);
+
         canvas->restore();
     } else {
         r.set(0, 0, SkIntToScalar(100), SkIntToScalar(100));
@@ -81,6 +100,8 @@
 
 //    return;
 
+    dump_layers("outside layer alpha", canvas);
+
     // now apply an effect
     SkMatrix m;
     m.setScale(SK_Scalar1, -SK_Scalar1);
diff --git a/tests/CanvasTest.cpp b/tests/CanvasTest.cpp
index 284e3cd..02b875e 100644
--- a/tests/CanvasTest.cpp
+++ b/tests/CanvasTest.cpp
@@ -46,6 +46,7 @@
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkClipStack.h"
+#include "SkDevice.h"
 #include "SkDocument.h"
 #include "SkMatrix.h"
 #include "SkNWayCanvas.h"
@@ -497,40 +498,6 @@
 }
 TEST_STEP(NestedSaveRestoreWithFlush, NestedSaveRestoreWithFlushTestStep);
 
-class CanvasTestingAccess {
-public:
-    static bool SameState(const SkCanvas* canvas1, const SkCanvas* canvas2) {
-        SkCanvas::LayerIter layerIter1(const_cast<SkCanvas*>(canvas1), false);
-        SkCanvas::LayerIter layerIter2(const_cast<SkCanvas*>(canvas2), false);
-        while (!layerIter1.done() && !layerIter2.done()) {
-            if (layerIter1.matrix() != layerIter2.matrix()) {
-                return false;    
-            }
-            if (layerIter1.clip() != layerIter2.clip()) {
-                return false;    
-            }
-            if (layerIter1.paint() != layerIter2.paint()) {
-                return false;   
-            }
-            if (layerIter1.x() != layerIter2.x()) {
-                return false;    
-            }
-            if (layerIter1.y() != layerIter2.y()) {
-                return false;
-            }
-            layerIter1.next();
-            layerIter2.next();
-        }
-        if (!layerIter1.done()) {
-            return false;
-        }
-        if (!layerIter2.done()) {
-            return false;
-        }
-        return true;
-    }
-};
-
 static void AssertCanvasStatesEqual(skiatest::Reporter* reporter, const TestData& d,
                                     const SkCanvas* canvas1, const SkCanvas* canvas2,
                                     CanvasTestStep* testStep) {
@@ -561,9 +528,27 @@
         canvas2->getTotalMatrix(), testStep->assertMessage());
     REPORTER_ASSERT_MESSAGE(reporter, equal_clips(*canvas1, *canvas2), testStep->assertMessage());
 
-    REPORTER_ASSERT_MESSAGE(reporter, 
-                            CanvasTestingAccess::SameState(canvas1, canvas2),
-                            testStep->assertMessage());
+    SkCanvas::LayerIter layerIter1(const_cast<SkCanvas*>(canvas1), false);
+    SkCanvas::LayerIter layerIter2(const_cast<SkCanvas*>(canvas2), false);
+    while (!layerIter1.done() && !layerIter2.done()) {
+        REPORTER_ASSERT_MESSAGE(reporter, layerIter1.matrix() ==
+            layerIter2.matrix(), testStep->assertMessage());
+        REPORTER_ASSERT_MESSAGE(reporter, layerIter1.clip() ==
+            layerIter2.clip(), testStep->assertMessage());
+        REPORTER_ASSERT_MESSAGE(reporter, layerIter1.paint() ==
+            layerIter2.paint(), testStep->assertMessage());
+        REPORTER_ASSERT_MESSAGE(reporter, layerIter1.x() ==
+            layerIter2.x(), testStep->assertMessage());
+        REPORTER_ASSERT_MESSAGE(reporter, layerIter1.y() ==
+            layerIter2.y(), testStep->assertMessage());
+        layerIter1.next();
+        layerIter2.next();
+    }
+    REPORTER_ASSERT_MESSAGE(reporter, layerIter1.done(),
+        testStep->assertMessage());
+    REPORTER_ASSERT_MESSAGE(reporter, layerIter2.done(),
+        testStep->assertMessage());
+
 }
 
 static void TestPdfDevice(skiatest::Reporter* reporter,
diff --git a/tools/VisualBench/WrappedBenchmark.h b/tools/VisualBench/WrappedBenchmark.h
index ddf601d..bd88f13 100644
--- a/tools/VisualBench/WrappedBenchmark.h
+++ b/tools/VisualBench/WrappedBenchmark.h
@@ -9,6 +9,7 @@
 #define WrappedBenchmark_DEFINED
 
 #include "Benchmark.h"
+#include "SkDevice.h"
 #include "SkSurface.h"
 #include "GrContext.h"
 #include "GrRenderTarget.h"
@@ -112,15 +113,26 @@
 
     void onBlitToScreen(SkCanvas* canvas, int w, int h) override {
         // We call copySurface directly on the underlying GPU surfaces for a more efficient blit.
-        GrRenderTarget* dst = canvas->internal_private_accessTopLayerRenderTarget();
-        SkASSERT(dst);
+        GrRenderTarget* dst, *src;
 
-        GrRenderTarget* src = fOffScreen->getCanvas()->internal_private_accessTopLayerRenderTarget();
-        SkASSERT(src);
+        SkCanvas::LayerIter canvasIter(canvas, false);
+        SkAssertResult((dst = canvasIter.device()->accessRenderTarget()));
+
+        SkCanvas::LayerIter offscreenIter(fOffScreen->getCanvas(), false);
+        SkAssertResult((src = offscreenIter.device()->accessRenderTarget()));
 
         SkASSERT(dst->getContext() == src->getContext());
 
         dst->getContext()->copySurface(dst, src, SkIRect::MakeWH(w, h), SkIPoint::Make(0, 0));
+
+#ifdef SK_DEBUG
+        // This method should not be called while layers are saved.
+        canvasIter.next();
+        SkASSERT(canvasIter.done());
+
+        offscreenIter.next();
+        SkASSERT(offscreenIter.done());
+#endif
     }
 
     int fNumSamples;