Re-land: cc: Cancel and re-prioritize worker pool tasks.

cc/resources/managed_tile_state.h

Index: cc/resources/managed_tile_state.h
diff --git a/cc/resources/managed_tile_state.h b/cc/resources/managed_tile_state.h
index f92505329ad673c2a29e22a1688677aa1a90a4b3..ee547225f7943670d0477937b3f180a9d6287082 100644
--- a/cc/resources/managed_tile_state.h
+++ b/cc/resources/managed_tile_state.h
@@ -8,6 +8,7 @@
 #include "base/hash_tables.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/resources/platform_color.h"
+#include "cc/resources/raster_worker_pool.h"
 #include "cc/resources/resource_pool.h"
 #include "cc/resources/resource_provider.h"
 #include "cc/resources/tile_manager.h"
@@ -110,11 +111,11 @@ class CC_EXPORT ManagedTileState {
   scoped_ptr<base::Value> AsValue() const;
 
   // Persisted state: valid all the time.
-  typedef base::hash_set<uint32_t> PixelRefSet;
-  PixelRefSet decoded_pixel_refs;
+  TileManager::PixelRefSet decoded_pixel_refs;
   DrawingInfo drawing_info;
-  PicturePileImpl::Analysis picture_pile_analysis;
   bool picture_pile_analyzed;
+  PicturePileImpl::Analysis picture_pile_analysis;
+  RasterWorkerPool::Task raster_task;
 
   // Ephemeral state, valid only during TileManager::ManageTiles.
   bool is_in_never_bin_on_both_trees() const {