Make PixelRefUtils::GatherDiscardablePixelRefs use Skia's version of the NoSaveLayerCanvas

skia/skia_library.gypi

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 
 # This gypi file contains the Skia library.
 # In component mode (shared_lib) it is folded into a single shared library with
 # the Chrome-specific enhancements but in all other cases it is a separate lib.
 
 # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!WARNING!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
@@ skipping 48 matching lines @@
     '../third_party/skia/src/ports/SkTLS_win.cpp',
 
     '../third_party/skia/src/sfnt/SkOTTable_name.cpp',
     '../third_party/skia/src/sfnt/SkOTTable_name.h',
     '../third_party/skia/src/sfnt/SkOTUtils.cpp',
     '../third_party/skia/src/sfnt/SkOTUtils.h',
 
     '../third_party/skia/include/utils/mac/SkCGUtils.h',
     '../third_party/skia/include/utils/SkDeferredCanvas.h',
     '../third_party/skia/include/utils/SkMatrix44.h',
+    '../third_party/skia/include/utils/SkNoSaveLayerCanvas.h',
     '../third_party/skia/src/utils/debugger/SkDebugCanvas.cpp',
     '../third_party/skia/src/utils/debugger/SkDebugCanvas.h',
     '../third_party/skia/src/utils/debugger/SkDrawCommand.cpp',
     '../third_party/skia/src/utils/debugger/SkDrawCommand.h',
     '../third_party/skia/src/utils/debugger/SkObjectParser.cpp',
     '../third_party/skia/src/utils/debugger/SkObjectParser.h',
     '../third_party/skia/src/utils/mac/SkCreateCGImageRef.cpp',
     '../third_party/skia/src/utils/SkBase64.cpp',
     '../third_party/skia/src/utils/SkBase64.h',
     '../third_party/skia/src/utils/SkBitSet.cpp',
@@ skipping 245 matching lines @@
       '../third_party/skia/include/pdf',
       '../third_party/skia/include/gpu',
       '../third_party/skia/include/lazy',
       '../third_party/skia/include/pathops',
       '../third_party/skia/include/pipe',
       '../third_party/skia/include/ports',
       '../third_party/skia/include/utils',
     ],
   },
 }