Add stable id to PaintImage.

cc/trees/layer_tree_host_pixeltest_masks.cc

 // 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.
 
 #include <stddef.h>
 
 #include "build/build_config.h"
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/picture_image_layer.h"
 #include "cc/layers/picture_layer.h"
@@ skipping 93 matching lines @@
   mask->SetBounds(mask_bounds);
 
   sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(200, 200);
   SkCanvas* canvas = surface->getCanvas();
   canvas->scale(SkIntToScalar(4), SkIntToScalar(4));
   MaskContentLayerClient client(mask_bounds);
   scoped_refptr<DisplayItemList> mask_display_list =
       client.PaintContentsToDisplayList(
           ContentLayerClient::PAINTING_BEHAVIOR_NORMAL);
   mask_display_list->Raster(canvas);
-  mask->SetImage(PaintImage(surface->makeImageSnapshot()));
+  mask->SetImage(
+      PaintImage(PaintImage::GetNextId(), surface->makeImageSnapshot()));
 
   scoped_refptr<SolidColorLayer> green = CreateSolidColorLayerWithBorder(
       gfx::Rect(25, 25, 50, 50), kCSSGreen, 1, SK_ColorBLACK);
   green->SetMaskLayer(mask.get());
   background->AddChild(green);
 
   RunPixelResourceTest(
       background, base::FilePath(FILE_PATH_LITERAL("image_mask_of_layer.png")));
 }
 
@@ skipping 272 matching lines @@
 
   RunPixelResourceTest(background,
                        base::FilePath(
                            FILE_PATH_LITERAL("mask_of_layer_with_blend.png")));
 }
 
 }  // namespace
 }  // namespace cc
 
 #endif  // !defined(OS_ANDROID)