Update from https://crrev.com/311145

cc/resources/raster_tile_priority_queue.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_RESOURCES_RASTER_TILE_PRIORITY_QUEUE_H_
 #define CC_RESOURCES_RASTER_TILE_PRIORITY_QUEUE_H_
 
 #include <set>
 #include <utility>
 #include <vector>
 
 #include "cc/base/cc_export.h"
 #include "cc/layers/picture_layer_impl.h"
 #include "cc/resources/tile_priority.h"
 #include "cc/resources/tiling_set_raster_queue.h"
 
 namespace cc {
 
+// TODO(vmpstr): Consider virtualizing this and adding ::Create with the
+// parameters of ::Build that would create a simpler queue for required only
+// tiles (ie, there's no need for the heap if all we're interested in are the
+// required tiles.
 class CC_EXPORT RasterTilePriorityQueue {
  public:
-  struct PairedTilingSetQueue {
+  enum class Type { ALL, REQUIRED_FOR_ACTIVATION, REQUIRED_FOR_DRAW };
+
+  class PairedTilingSetQueue {
+   public:
     PairedTilingSetQueue();
     PairedTilingSetQueue(const PictureLayerImpl::Pair& layer_pair,
-                         TreePriority tree_priority);
+                         TreePriority tree_priority,
+                         Type type);
     ~PairedTilingSetQueue();
 
     bool IsEmpty() const;
     Tile* Top(TreePriority tree_priority);
     void Pop(TreePriority tree_priority);
 
     WhichTree NextTileIteratorTree(TreePriority tree_priority) const;
     void SkipTilesReturnedByTwin(TreePriority tree_priority);
 
     scoped_refptr<base::debug::ConvertableToTraceFormat> StateAsValue() const;
 
-    scoped_ptr<TilingSetRasterQueue> active_queue;
-    scoped_ptr<TilingSetRasterQueue> pending_queue;
-    bool has_both_layers;
+    const TilingSetRasterQueue* active_queue() const {
+      return active_queue_.get();
+    }
+    const TilingSetRasterQueue* pending_queue() const {
+      return pending_queue_.get();
+    }
+
+   private:
+    scoped_ptr<TilingSetRasterQueue> active_queue_;
+    scoped_ptr<TilingSetRasterQueue> pending_queue_;
+    bool has_both_layers_;
 
     // Set of returned tiles (excluding the current one) for DCHECKing.
-    std::set<const Tile*> returned_tiles_for_debug;
+    std::set<const Tile*> returned_tiles_for_debug_;
   };
 
   RasterTilePriorityQueue();
   ~RasterTilePriorityQueue();
 
   void Build(const std::vector<PictureLayerImpl::Pair>& paired_layers,
-             TreePriority tree_priority);
+             TreePriority tree_priority,
+             Type type);
   void Reset();
 
   bool IsEmpty() const;
   Tile* Top();
   void Pop();
 
  private:
   // TODO(vmpstr): This is potentially unnecessary if it becomes the case that
   // PairedTilingSetQueue is fast enough to copy. In that case, we can use
   // objects directly (ie std::vector<PairedTilingSetQueue>.
   ScopedPtrVector<PairedTilingSetQueue> paired_queues_;
   TreePriority tree_priority_;
 
   DISALLOW_COPY_AND_ASSIGN(RasterTilePriorityQueue);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_RASTER_TILE_PRIORITY_QUEUE_H_