cc: Don't discard tiles unless memory is low

cc/picture_layer_tiling.h

 // Copyright 2012 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_PICTURE_LAYER_TILING_H_
 #define CC_PICTURE_LAYER_TILING_H_
 
 #include "base/basictypes.h"
 #include "base/hash_tables.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 18 matching lines @@
     PictureLayerTiling* tiling,
     gfx::Rect content_rect) = 0;
   virtual void UpdatePile(Tile* tile) = 0;
   virtual gfx::Size CalculateTileSize(
     gfx::Size current_tile_size,
     gfx::Size content_bounds) = 0;
 };
 
 class TileHandle {
  public:
-  TileHandle(scoped_refptr<Tile> tile);
-  Tile* tile() const { return tile_.get(); }
+  TileHandle(std::pair<int, int> key, scoped_refptr<Tile> tile);
+  TileHandle(const TileHandle& tile_handle);
+  ~TileHandle();
+
   void RegisterWithTileManager();
   void UnregisterFromTileManager();
+
+  void AddToLiveTileList(PictureLayerTiling* tiling);
+  void RemoveFromLiveTileList();
+
+  std::pair<int, int> key() const { return key_; }
+  Tile* tile() const { return tile_.get(); }
+  bool should_be_live() const { return should_be_live_; }
+  void set_should_be_live(bool should_be_live) {
+    should_be_live_ = should_be_live;
+  }
+
  private:
+  std::pair<int, int> key_;
   scoped_refptr<Tile> tile_;
   scoped_refptr<ManagedTileState> managed_tile_state_;
+
+  // Transiently set in UpdateTilePriorities to track tiles that
+  // are actively desired to be painted.
+  bool should_be_live_;
+
+  // tiling_ is non-NULL only if this is in a tiling's live_tile_list_, in
+  // which case tiling_live_tile_list_iterator_ valid.
+  PictureLayerTiling* tiling_;
+  std::list<TileHandle*>::iterator tiling_live_tile_list_iterator_;
 };
 
 class CC_EXPORT PictureLayerTiling {
  public:
   ~PictureLayerTiling();
 
   // Create a tiling with no tiles.  CreateTiles must be called to add some.
   static scoped_ptr<PictureLayerTiling> Create(float contents_scale);
   scoped_ptr<PictureLayerTiling> Clone() const;
 
@@ skipping 104 matching lines @@
   // Copies the src_tree priority into the dst_tree priority for all tiles.
   // The src_tree priority is reset to the lowest priority possible.  This
   // also updates the pile on each tile to be the current client's pile.
   void DidBecomeActive();
 
   scoped_ptr<base::Value> AsValue() const;
 
  protected:
   typedef std::pair<int, int> TileMapKey;
   typedef base::hash_map<TileMapKey, TileHandle> TileMap;
+  typedef std::list<TileHandle*> TileList;
 
   PictureLayerTiling(float contents_scale);
   Tile* TileAt(int, int) const;
   void CreateTilesFromContentRect(gfx::Rect layer_rect);
   void CreateTile(int i, int j);
 
   PictureLayerTilingClient* client_;
   float contents_scale_;
   gfx::Size layer_bounds_;
   gfx::Rect last_prioritized_rect_;
   // It is not legal to have a NULL tile in the tiles_ map.
   TileMap tiles_;
+  TileList live_tiles_;
   TilingData tiling_data_;
   TileResolution resolution_;
   int last_source_frame_number_;
   double last_impl_frame_time_;
 
+  friend class TileHandle;
   friend class Iterator;
 };
 
 }  // namespace cc
 
 #endif  // CC_PICTURE_LAYER_TILING_H_