cc: Do not cleanup tiles with raster tasks.

cc/resources/tile.h

Index: cc/resources/tile.h
diff --git a/cc/resources/tile.h b/cc/resources/tile.h
index 9aeabfa190ae9b85b7ab1f6f1e595a361d9d9c62..9bdd60926785d537f6b131c36b685db470f05b58 100644
--- a/cc/resources/tile.h
+++ b/cc/resources/tile.h
@@ -20,6 +20,9 @@ namespace cc {
 
 class CC_EXPORT Tile : public RefCountedManaged<Tile> {
  public:
+  // Needed by ScopedVector for deleting released tiles.
+  ~Tile();
+
   enum TileRasterFlags { USE_PICTURE_ANALYSIS = 1 << 0 };
 
   typedef uint64 Id;
@@ -168,12 +171,13 @@ class CC_EXPORT Tile : public RefCountedManaged<Tile> {
        int layer_id,
        int source_frame_number,
        int flags);
-  ~Tile();
 
   ManagedTileState& managed_state() { return managed_state_; }
   const ManagedTileState& managed_state() const { return managed_state_; }
   RasterMode DetermineRasterModeForResolution(TileResolution resolution) const;
 
+  bool HasRasterTask() const;
+
   TileManager* tile_manager_;
   scoped_refptr<PicturePileImpl> picture_pile_;
   gfx::Rect tile_size_;