cc: Do not cleanup tiles with raster tasks.

cc/resources/picture_layer_tiling.cc

Index: cc/resources/picture_layer_tiling.cc
diff --git a/cc/resources/picture_layer_tiling.cc b/cc/resources/picture_layer_tiling.cc
index fdfbad9f62e3e60bbd1949541123ef36c5713de1..af4f2b40a4dd4d5ddb177c528a7a1974a6dacd30 100644
--- a/cc/resources/picture_layer_tiling.cc
+++ b/cc/resources/picture_layer_tiling.cc
@@ -94,6 +94,8 @@ PictureLayerTiling::PictureLayerTiling(float contents_scale,
 }
 
 PictureLayerTiling::~PictureLayerTiling() {
+  for (TileMap::const_iterator it = tiles_.begin(); it != tiles_.end(); ++it)
+    it->second.get()->SetPriority(client_->GetTree(), TilePriority());
 }
 
 void PictureLayerTiling::SetClient(PictureLayerTilingClient* client) {
@@ -214,6 +216,11 @@ void PictureLayerTiling::DoInvalidate(const Region& layer_region,
       TileMap::iterator find = tiles_.find(key);
       if (find == tiles_.end())
         continue;
+
+      // Reset priority as tile is ref-counted and might still be used
+      // even though we no longer hold a reference to it here anymore.
+      find->second.get()->SetPriority(client_->GetTree(), TilePriority());

[reveman, 2014/07/25 17:00:54]

This comment is relevant not just here but in all cases where you drop a tile
reference. Maybe you can add a "void ReleaseTile(Tile* tile, WhichTree tree)"
utility function to the anonymous namespace that will reset the priority and
contain this comment.

[sohanjg, 2014/07/26 09:36:01]

I have added the comment in all the places for now, will move to a new func as a
follow up for sure.

[reveman, 2014/07/28 02:24:35]

I don't think that makes sense as a follow up. Please move it to a function in
this patch rather than duplicating code.

[sohanjg, 2014/07/28 10:10:19]

Done.

+
       tiles_.erase(find);
       new_tile_keys.push_back(key);
     }
@@ -598,8 +605,10 @@ void PictureLayerTiling::SetLiveTilesRect(
     TileMap::iterator found = tiles_.find(key);
     // If the tile was outside of the recorded region, it won't exist even
     // though it was in the live rect.
-    if (found != tiles_.end())
+    if (found != tiles_.end()) {
+      found->second.get()->SetPriority(client_->GetTree(), TilePriority());
       tiles_.erase(found);
+    }
   }
 
   const PictureLayerTiling* twin_tiling = client_->GetTwinTiling(this);