cc: More consistent reasoning about display list memory usage.

cc/playback/display_item_list.h

 // Copyright 2014 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_PLAYBACK_DISPLAY_ITEM_LIST_H_
 #define CC_PLAYBACK_DISPLAY_ITEM_LIST_H_
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 52 matching lines @@
   // (since the data may already have been incorporated into cached picture
   // sizes, etc).
   void RemoveLast();
 
   // Called after all items are appended, to process the items and, if
   // applicable, create an internally cached SkPicture.
   void Finalize();
 
   bool IsSuitableForGpuRasterization() const;
   int ApproximateOpCount() const;
-  size_t PictureMemoryUsage() const;
+  size_t ApproximateMemoryUsage() const;
 
   bool RetainsIndividualDisplayItems() const;
 
   scoped_refptr<base::trace_event::ConvertableToTraceFormat> AsValue(
       bool include_items) const;
 
   void EmitTraceSnapshot() const;
 
   void GatherPixelRefs(const gfx::Size& grid_cell_size);
 
@@ skipping 23 matching lines @@
   skia::RefPtr<SkPicture> picture_;
 
   scoped_ptr<SkPictureRecorder> recorder_;
   skia::RefPtr<SkCanvas> canvas_;
   bool use_cached_picture_;
   bool retain_individual_display_items_;
 
   gfx::Rect layer_rect_;
   bool is_suitable_for_gpu_rasterization_;
   int approximate_op_count_;
+
+  // Memory usage due to the cached SkPicture.
   size_t picture_memory_usage_;
 
+  // Memory usage due to external data held by display items.
+  size_t external_memory_usage_;
+
   scoped_ptr<PixelRefMap> pixel_refs_;
 
   friend class base::RefCountedThreadSafe<DisplayItemList>;
   friend class PixelRefMap::Iterator;
-  FRIEND_TEST_ALL_PREFIXES(DisplayItemListTest, PictureMemoryUsage);
+  FRIEND_TEST_ALL_PREFIXES(DisplayItemListTest, ApproximateMemoryUsage);
   DISALLOW_COPY_AND_ASSIGN(DisplayItemList);
 };
 
 }  // namespace cc
 
 #endif  // CC_PLAYBACK_DISPLAY_ITEM_LIST_H_