cc: Remove tile sharing from tilings.

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 34e7defd99bd40c0e8fc3fbaa610ce4a5411cc00..586fe9c9966df8def825f4e788c1d28ce8b85bb8 100644
--- a/cc/resources/picture_layer_tiling.h
+++ b/cc/resources/picture_layer_tiling.h
@@ -77,8 +77,10 @@ class CC_EXPORT PictureLayerTiling {
   void Invalidate(const Region& layer_invalidation);
   void SetRasterSourceOnTiles();
   void CreateMissingTilesInLiveTilesRect();
+  void TakeTilesAndPropertiesFrom(PictureLayerTiling* pending_twin);
 
-  void CloneTilesAndPropertiesFrom(const PictureLayerTiling& twin_tiling);
+  bool IsTileRequiredForActivation(const Tile* tile) const;
+  bool IsTileRequiredForDraw(const Tile* tile) const;
 
   void set_resolution(TileResolution resolution) { resolution_ = resolution; }
   TileResolution resolution() const { return resolution_; }
@@ -95,34 +97,30 @@ class CC_EXPORT PictureLayerTiling {
 
   Tile* TileAt(int i, int j) const {
     TileMap::const_iterator iter = tiles_.find(TileMapKey(i, j));
-    return (iter == tiles_.end()) ? NULL : iter->second.get();
+    return iter == tiles_.end() ? nullptr : iter->second.get();
   }
 
+  // For testing functionality.
   void CreateAllTilesForTesting() {
     SetLiveTilesRect(gfx::Rect(tiling_data_.tiling_size()));
   }
-
   const TilingData& TilingDataForTesting() const { return tiling_data_; }
-
   std::vector<Tile*> AllTilesForTesting() const {
     std::vector<Tile*> all_tiles;
     for (TileMap::const_iterator it = tiles_.begin(); it != tiles_.end(); ++it)
       all_tiles.push_back(it->second.get());
     return all_tiles;
   }
-
   void UpdateAllTilePrioritiesForTesting() {
     for (TileMap::const_iterator it = tiles_.begin(); it != tiles_.end(); ++it)
       UpdateTileAndTwinPriority(it->second.get());
   }
-
   std::vector<scoped_refptr<Tile>> AllRefTilesForTesting() const {
     std::vector<scoped_refptr<Tile>> all_tiles;
     for (TileMap::const_iterator it = tiles_.begin(); it != tiles_.end(); ++it)
       all_tiles.push_back(it->second);
     return all_tiles;
   }
-
   void SetAllTilesOccludedForTesting() {
     gfx::Rect viewport_in_layer_space =
         ScaleToEnclosingRect(current_visible_rect_, 1.0f / contents_scale_);
@@ -131,37 +129,10 @@ class CC_EXPORT PictureLayerTiling {
                   SimpleEnclosedRegion(viewport_in_layer_space),
                   SimpleEnclosedRegion(viewport_in_layer_space));
   }
-
   const gfx::Rect& GetCurrentVisibleRectForTesting() const {
     return current_visible_rect_;
   }
 
-  bool IsTileOccluded(const Tile* tile) const;
-  bool IsTileRequiredForActivationIfVisible(const Tile* tile) const;
-  bool IsTileRequiredForDrawIfVisible(const Tile* tile) const;
-
-  void UpdateTileAndTwinPriority(Tile* tile) const;
-  TilePriority ComputePriorityForTile(const Tile* tile) const;
-  void UpdateRequiredStateForTile(Tile* tile, WhichTree tree) const;
-  bool has_visible_rect_tiles() const { return has_visible_rect_tiles_; }
-  bool has_skewport_rect_tiles() const { return has_skewport_rect_tiles_; }
-  bool has_soon_border_rect_tiles() const {
-    return has_soon_border_rect_tiles_;
-  }
-  bool has_eventually_rect_tiles() const { return has_eventually_rect_tiles_; }
-
-  const gfx::Rect& current_visible_rect() const {
-    return current_visible_rect_;
-  }
-  const gfx::Rect& current_skewport_rect() const {
-    return current_skewport_rect_;
-  }
-  const gfx::Rect& current_soon_border_rect() const {
-    return current_soon_border_rect_;
-  }
-  const gfx::Rect& current_eventually_rect() const {
-    return current_eventually_rect_;
-  }
   void VerifyAllTilesHaveCurrentRasterSource() const;
 
   // Iterate over all tiles to fill content_rect.  Even if tiles are invalid
@@ -236,10 +207,6 @@ class CC_EXPORT PictureLayerTiling {
       const gfx::Rect& bounding_rect,
       RectExpansionCache* cache);
 
-  bool has_ever_been_updated() const {
-    return visible_rect_history_[0].frame_time_in_seconds != 0.0;
-  }
-
  protected:
   friend class CoverageIterator;
   friend class TilingSetRasterQueueAll;
@@ -262,12 +229,10 @@ class CC_EXPORT PictureLayerTiling {
                      int skewport_extrapolation_limit_in_content_pixels);
   void SetLiveTilesRect(const gfx::Rect& live_tiles_rect);
   void VerifyLiveTilesRect(bool is_on_recycle_tree) const;
-  Tile* CreateTile(int i,
-                   int j,
-                   const PictureLayerTiling* twin_tiling,
-                   PictureLayerTiling* recycled_twin);
+  Tile* CreateTile(int i, int j);
   // Returns true if the Tile existed and was removed from the tiling.
-  bool RemoveTileAt(int i, int j, PictureLayerTiling* recycled_twin);
+  bool RemoveTileAt(int i, int j);
+  bool TilingMatchesTileIndices(const PictureLayerTiling* twin) const;
 
   // Computes a skewport. The calculation extrapolates the last visible
   // rect and the current visible rect to expand the skewport to where it
@@ -278,12 +243,12 @@ class CC_EXPORT PictureLayerTiling {
       const;
 
   // Save the required data for computing tile priorities later.
-  void UpdateTilePriorityRects(float content_to_screen_scale_,
-                               const gfx::Rect& visible_rect_in_content_space,
-                               const gfx::Rect& skewport,
-                               const gfx::Rect& soon_border_rect,
-                               const gfx::Rect& eventually_rect,
-                               const Occlusion& occlusion_in_layer_space);
+  void SetTilePriorityRects(float content_to_screen_scale_,
+                            const gfx::Rect& visible_rect_in_content_space,
+                            const gfx::Rect& skewport,
+                            const gfx::Rect& soon_border_rect,
+                            const gfx::Rect& eventually_rect,
+                            const Occlusion& occlusion_in_layer_space);
 
   void UpdateTilePriorityForTree(Tile* tile, WhichTree tree) const;
   bool NeedsUpdateForFrameAtTimeAndViewport(
@@ -304,6 +269,42 @@ class CC_EXPORT PictureLayerTiling {
     if (visible_rect_history_[1].frame_time_in_seconds == 0.0)
       visible_rect_history_[1] = visible_rect_history_[0];
   }
+  bool IsTileOccludedOnCurrentTree(const Tile* tile) const;
+  bool ShouldCreateTileAt(int i, int j) const;
+  bool IsTileOccluded(const Tile* tile) const;
+  void UpdateTileAndTwinPriority(Tile* tile) const;
+  TilePriority ComputePriorityForTile(const Tile* tile) const;
+  bool has_visible_rect_tiles() const { return has_visible_rect_tiles_; }
+  bool has_skewport_rect_tiles() const { return has_skewport_rect_tiles_; }
+  bool has_soon_border_rect_tiles() const {
+    return has_soon_border_rect_tiles_;
+  }
+  bool has_eventually_rect_tiles() const { return has_eventually_rect_tiles_; }
+
+  const gfx::Rect& current_visible_rect() const {
+    return current_visible_rect_;
+  }
+  const gfx::Rect& pending_visible_rect() const {
+    const PictureLayerTiling* twin =

[enne (OOO), 2015/04/13 22:36:02]

This needs a serious comment.  It's still hard to keep in my brain that
pending_visible_rect can be the active visible rect if there's not a pending
twin.  And then this just *happens* to work out that in both the case where
there's no pending twin and where it's the pending layer that iterating using a
difference rect of visible to pending visible is a no-op.

[vmpstr, 2015/04/13 23:52:13]

Well... to be fair, it doesn't just happen, it was written that way. I've added
a comment. I'm also open to other suggestions of how to implement this. I don't
think adding comments like this makes anything any more clear. 

+        client_->GetTree() == ACTIVE_TREE
+            ? client_->GetPendingOrActiveTwinTiling(this)
+            : this;
+    if (twin)
+      return twin->current_visible_rect();
+    return current_visible_rect();
+  }
+  const gfx::Rect& current_skewport_rect() const {
+    return current_skewport_rect_;
+  }
+  const gfx::Rect& current_soon_border_rect() const {
+    return current_soon_border_rect_;
+  }
+  const gfx::Rect& current_eventually_rect() const {
+    return current_eventually_rect_;
+  }
+  bool has_ever_been_updated() const {
+    return visible_rect_history_[0].frame_time_in_seconds != 0.0;
+  }
 
   const size_t max_tiles_for_interest_area_;
   const float skewport_target_time_in_seconds_;