cc: Update discardable image metadata generation to get PaintImages.

cc/paint/discardable_image_store.h

Index: cc/paint/discardable_image_store.h
diff --git a/cc/paint/discardable_image_store.h b/cc/paint/discardable_image_store.h
new file mode 100644
index 0000000000000000000000000000000000000000..dec133a14489c8c9802490241d4dd528ec29cd99
--- /dev/null
+++ b/cc/paint/discardable_image_store.h
@@ -0,0 +1,49 @@
+// 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.
+
+#ifndef CC_PAINT_DISCARDABLE_IMAGE_STORE_H_
+#define CC_PAINT_DISCARDABLE_IMAGE_STORE_H_
+
+#include "cc/paint/paint_export.h"
+#include "cc/paint/paint_op_buffer.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "third_party/skia/include/core/SkMatrix.h"
+#include "third_party/skia/include/core/SkRect.h"
+
+namespace cc {
+class PaintFlags;
+class PaintImage;
+
+class CC_PAINT_EXPORT DiscardableImageStore {
+ public:
+  DiscardableImageStore(
+      int width,
+      int height,
+      std::vector<std::pair<DrawImage, gfx::Rect>>* image_set,
+      std::unordered_map<ImageId, gfx::Rect>* image_id_to_rect);
+  ~DiscardableImageStore();
+
+  void GatherDiscardableImages(const PaintOpBuffer* buffer);
+  SkCanvas* NoDrawCanvas();

[vmpstr, 2017/04/28 16:40:11]

nit: GetNoDrawCanvas() or just GetCanvas()? or canvas()? Is it important that
it's a no draw here? If so, make the return value SkNoDrawCanvas*

[Khushal, 2017/05/03 21:07:07]

The no draw part was just to make it clear that its shouldn't be used to
playback any draw ops. I was also considering just adding an iterator for the
DisplayItemList, similar to PaintOpBuffer, so we can do the iteration inside the
store itself and there is no need to expose the canvas. Would that be better?

[vmpstr, 2017/05/05 18:56:20]

I think we can do that second step as a follow up. For now, I would prefer if
the return type of the canvas was SkNoDrawCanvas to make it reaally clear and
name the function GetNoDrawCanvas.

[Khushal, 2017/05/05 21:54:12]

Done.

+
+ private:
+  class PaintTrackingCanvas;
+
+  void AddImageFromFlags(const SkRect& rect, const PaintFlags& flags);
+  void AddImage(const PaintImage& paint_image,
+                const SkRect& src_rect,
+                const SkRect& rect,
+                const SkMatrix* local_matrix,
+                const PaintFlags& flags);
+
+  // This canvas is used only for tracking transform/clip/filter state from the
+  // non-drawing ops.
+  std::unique_ptr<PaintTrackingCanvas> canvas_;
+  std::vector<std::pair<DrawImage, gfx::Rect>>* image_set_;
+  std::unordered_map<ImageId, gfx::Rect>* image_id_to_rect_;
+};
+
+}  // namespace cc
+
+#endif  // CC_PAINT_DISCARDABLE_IMAGE_STORE_H_