cc: Change TileManager iterators to be queues.

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 <utility>
+#include <vector>
+
+#include "cc/base/cc_export.h"
+#include "cc/layers/picture_layer_impl.h"
+#include "cc/resources/tile_priority.h"
+
+namespace cc {
+
+class CC_EXPORT RasterTilePriorityQueue {
+ public:
+  struct PairedPictureLayerQueue {
+    PairedPictureLayerQueue();
+    PairedPictureLayerQueue(const PictureLayerImpl::Pair& layer_pair,
+                            TreePriority tree_priority);
+    ~PairedPictureLayerQueue();
+
+    bool IsEmpty() const;
+    Tile* Top(TreePriority tree_priority);
+    void Pop(TreePriority tree_priority);
+
+    PictureLayerImpl::LayerRasterTileIterator* NextTileIterator(
+        TreePriority tree_priority);
+
+    PictureLayerImpl::LayerRasterTileIterator active_iterator;
+    PictureLayerImpl::LayerRasterTileIterator pending_iterator;
+
+    // TODO(vmpstr): Investigate removing this.
+    std::vector<Tile*> returned_shared_tiles;
+  };
+
+  RasterTilePriorityQueue();
+  ~RasterTilePriorityQueue();
+
+  void Build(const std::vector<PictureLayerImpl::Pair>& paired_layers,
+             TreePriority tree_priority);
+  void Reset();
+
+  bool IsEmpty() const;
+  Tile* Top();
+  void Pop();
+
+ private:
+  std::vector<PairedPictureLayerQueue> paired_queues_;
+  TreePriority tree_priority_;
+
+  DISALLOW_COPY_AND_ASSIGN(RasterTilePriorityQueue);
+};
+
+}  // namespace cc
+
+#endif  // CC_RESOURCES_RASTER_TILE_PRIORITY_QUEUE_H_