Revert of cc: Remove tile sharing from tilings.

cc/resources/tile_manager.cc

Index: cc/resources/tile_manager.cc
diff --git a/cc/resources/tile_manager.cc b/cc/resources/tile_manager.cc
index 8bf6120421715ef35478b67dbfabaa31c7bd8882..b98b7a6e6399d528701a1440b6debc9c422f2f00 100644
--- a/cc/resources/tile_manager.cc
+++ b/cc/resources/tile_manager.cc
@@ -451,7 +451,7 @@
       break;
 
     Tile* tile = eviction_priority_queue->Top();
-    if (!other_priority.IsHigherPriorityThan(tile->priority()))
+    if (!other_priority.IsHigherPriorityThan(tile->combined_priority()))
       break;
 
     *usage -= MemoryUsage::FromTile(tile);
@@ -506,7 +506,7 @@
   scoped_ptr<EvictionTilePriorityQueue> eviction_priority_queue;
   for (; !raster_priority_queue->IsEmpty(); raster_priority_queue->Pop()) {
     Tile* tile = raster_priority_queue->Top();
-    TilePriority priority = tile->priority();
+    TilePriority priority = tile->combined_priority();
 
     if (TilePriorityViolatesMemoryPolicy(priority)) {
       TRACE_EVENT_INSTANT0(
@@ -698,9 +698,9 @@
 
   return make_scoped_refptr(new RasterTaskImpl(
       const_resource, tile->raster_source(), tile->content_rect(),
-      tile->contents_scale(), tile->priority().resolution, tile->layer_id(),
-      static_cast<const void*>(tile), tile->source_frame_number(),
-      tile->use_picture_analysis(),
+      tile->contents_scale(), tile->combined_priority().resolution,
+      tile->layer_id(), static_cast<const void*>(tile),
+      tile->source_frame_number(), tile->use_picture_analysis(),
       base::Bind(&TileManager::OnRasterTaskCompleted, base::Unretained(this),
                  tile->id(), base::Passed(&resource)),
       &decode_tasks));
@@ -805,15 +805,6 @@
     if (!raster_priority_queue->Top()->IsReadyToDraw())
       return false;
   }
-
-#if DCHECK_IS_ON()
-  scoped_ptr<RasterTilePriorityQueue> all_queue(
-      client_->BuildRasterQueue(global_state_.tree_priority, type));
-  for (; !all_queue->IsEmpty(); all_queue->Pop()) {
-    auto* tile = all_queue->Top();
-    DCHECK_IMPLIES(tile->required_for_activation(), tile->IsReadyToDraw());
-  }
-#endif
   return true;
 }
 bool TileManager::IsReadyToActivate() const {