cc: Start using raster/eviction iterators.

cc/resources/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_TILE_PRIORITY_QUEUE_H_
+#define CC_RESOURCES_TILE_PRIORITY_QUEUE_H_
+
+#include <vector>
+
+namespace cc {
+
+class PictureLayerImpl;
+class Tile;
+
+class TilePriorityQueue {
+ public:
+  virtual void Pop() = 0;
+  virtual bool IsEmpty() = 0;
+  virtual Tile* Top() = 0;
+
+ protected:
+  struct PairedPictureLayer {
+    PairedPictureLayer();
+    ~PairedPictureLayer();
+
+    PictureLayerImpl* active_layer;
+    PictureLayerImpl* pending_layer;
+  };
+
+  virtual ~TilePriorityQueue();
+
+  // Given a set of layers and an empty paired_layers output vector, this will
+  // construct pairs out of layers so that twin layers will appear in the same
+  // picture pair.
+  void GetPairedPictureLayers(
+      const std::vector<PictureLayerImpl*>& layers,
+      std::vector<PairedPictureLayer>* paired_layers) const;
+};
+
+}  // namespace cc
+
+#endif  // CC_RESOURCES_TILE_PRIORITY_QUEUE_H_