Add stable id to PaintImage.

cc/paint/discardable_image_store.cc

 // Copyright 2017 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 "cc/paint/discardable_image_store.h"
 
 #include "base/containers/adapters.h"
 #include "base/memory/ptr_util.h"
 #include "cc/paint/display_item_list.h"
 #include "third_party/skia/include/utils/SkNoDrawCanvas.h"
@@ skipping 57 matching lines @@
   std::vector<SkPaint> saved_paints_;
 };
 
 DiscardableImageStore::DiscardableImageStore(
     int width,
     int height,
     std::vector<std::pair<DrawImage, gfx::Rect>>* image_set,
     base::flat_map<ImageId, gfx::Rect>* image_id_to_rect)
     : canvas_(base::MakeUnique<PaintTrackingCanvas>(width, height)),
       image_set_(image_set),
-      image_id_to_rect_(image_id_to_rect) {}
+      image_id_to_rect_(image_id_to_rect),
+      unknown_stable_id_(PaintImage::GetNextId()) {}
 
 DiscardableImageStore::~DiscardableImageStore() = default;
 
 SkNoDrawCanvas* DiscardableImageStore::GetNoDrawCanvas() {
   return canvas_.get();
 }
 
 void DiscardableImageStore::GatherDiscardableImages(
     const PaintOpBuffer* buffer) {
   if (!buffer->HasDiscardableImages())
@@ skipping 86 matching lines @@
 // embedded in SkPaints. Other embedded image cases, such as SkPictures,
 // are not yet handled.
 void DiscardableImageStore::AddImageFromFlags(const SkRect& rect,
                                               const PaintFlags& flags) {
   SkShader* shader = flags.getShader();
   if (shader) {
     SkMatrix matrix;
     SkShader::TileMode xy[2];
     SkImage* image = shader->isAImage(&matrix, xy);
     if (image) {
-      PaintImage paint_image(sk_ref_sp(image),
+      PaintImage paint_image(unknown_stable_id_, sk_ref_sp(image),
                              PaintImage::AnimationType::UNKNOWN,
                              PaintImage::CompletionState::UNKNOWN);
       // TODO(ericrk): Handle cases where we only need a sub-rect from the
       // image. crbug.com/671821
       AddImage(paint_image, SkRect::MakeFromIRect(image->bounds()), rect,
                &matrix, flags);
     }
   }
 }
 
@@ skipping 49 matching lines @@
 
   // TODO(khushalsagar): Keep PaintImage in DrawImage.
   (*image_id_to_rect_)[sk_image->uniqueID()].Union(image_rect);
   image_set_->push_back(
       std::make_pair(DrawImage(std::move(sk_image), src_irect, filter_quality,
                                matrix, target_color_space),
                      image_rect));
 }
 
 }  // namespace cc