[WIP] cc: Use reverse spiral iterator in tiling eviction.

cc/resources/picture_layer_tiling.h

Index: cc/resources/picture_layer_tiling.h
diff --git a/cc/resources/picture_layer_tiling.h b/cc/resources/picture_layer_tiling.h
index eb47b60ed61cf6736d1b58f6dd0773076942bb41..5bc978c92c4124afb63910b79b6b37adad76faaf 100644
--- a/cc/resources/picture_layer_tiling.h
+++ b/cc/resources/picture_layer_tiling.h
@@ -124,7 +124,8 @@ class CC_EXPORT PictureLayerTiling {
     TilingEvictionTileIterator();
     TilingEvictionTileIterator(PictureLayerTiling* tiling,
                                TreePriority tree_priority,
-                               EvictionCategory category);
+                               EvictionCategory category,
+                               bool skip_shared_high_priority_tiles);
     ~TilingEvictionTileIterator();
 
     operator bool() const;
@@ -133,8 +134,24 @@ class CC_EXPORT PictureLayerTiling {
     TilingEvictionTileIterator& operator++();
 
    private:
-    const std::vector<Tile*>* eviction_tiles_;
-    size_t current_eviction_tiles_index_;
+    void AdvanceEventually(bool* skipped_tiles);
+    void AdvanceSoon();
+    void AdvanceNow();
+    bool PrepareTileUnlessReturnedByTwin(Tile* tile) const;
+
+    PictureLayerTiling* tiling_;
+    TreePriority tree_priority_;
+    EvictionCategory eviction_category_;
+
+    bool processing_soon_border_rect_;
+    bool skip_shared_high_priority_tiles_;
+    std::vector<Tile*> unoccluded_now_tiles_;
+    size_t unoccluded_now_tiles_index_;
+
+    Tile* current_tile_;
+
+    TilingData::Iterator visible_iterator_;
+    TilingData::ReverseSpiralDifferenceIterator spiral_iterator_;
   };
 
   ~PictureLayerTiling();
@@ -322,10 +339,6 @@ class CC_EXPORT PictureLayerTiling {
                             const gfx::Rect& visible_rect_in_content_space)
       const;
 
-  void UpdateEvictionCacheIfNeeded(TreePriority tree_priority);
-  const std::vector<Tile*>* GetEvictionTiles(TreePriority tree_priority,
-                                             EvictionCategory category);
-
   void Invalidate(const Region& layer_region);
 
   void DoInvalidate(const Region& layer_region,
@@ -366,19 +379,6 @@ class CC_EXPORT PictureLayerTiling {
 
   Occlusion current_occlusion_in_layer_space_;
 
-  // TODO(reveman): Remove this in favour of an array of eviction_tiles_ when we
-  // change all enums to have a consistent way of getting the count/last
-  // element.
-  std::vector<Tile*> eviction_tiles_now_;
-  std::vector<Tile*> eviction_tiles_now_and_required_for_activation_;
-  std::vector<Tile*> eviction_tiles_soon_;
-  std::vector<Tile*> eviction_tiles_soon_and_required_for_activation_;
-  std::vector<Tile*> eviction_tiles_eventually_;
-  std::vector<Tile*> eviction_tiles_eventually_and_required_for_activation_;
-
-  bool eviction_tiles_cache_valid_;
-  TreePriority eviction_cache_tree_priority_;
-
  private:
   DISALLOW_ASSIGN(PictureLayerTiling);