Update from https://crrev.com/320343

cc/resources/tiling_set_raster_queue_all.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_TILING_SET_RASTER_QUEUE_ALL_H_
 #define CC_RESOURCES_TILING_SET_RASTER_QUEUE_ALL_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/resources/picture_layer_tiling_set.h"
 #include "cc/resources/tile.h"
 #include "cc/resources/tile_priority.h"
 
 namespace cc {
 
 // This queue returns all tiles required to be rasterized from HIGH_RESOLUTION
 // and LOW_RESOLUTION tilings.
 class CC_EXPORT TilingSetRasterQueueAll {
  public:
   TilingSetRasterQueueAll(PictureLayerTilingSet* tiling_set,
                           bool prioritize_low_res);
   ~TilingSetRasterQueueAll();
 
   Tile* Top();
   const Tile* Top() const;
   void Pop();
   bool IsEmpty() const;
 
  private:
+  // Helper base class for individual region iterators.
+  class OnePriorityRectIterator {
+   public:
+    OnePriorityRectIterator();
+    OnePriorityRectIterator(PictureLayerTiling* tiling,
+                            TilingData* tiling_data);
+
+    bool done() const { return !tile_; }
+    Tile* operator*() const { return tile_; }
+
+   protected:
+    ~OnePriorityRectIterator() = default;
+    bool TileNeedsRaster(Tile* tile) const {
+      return tile->NeedsRaster() && !tiling_->IsTileOccluded(tile);
+    }
+
+    template <typename TilingIteratorType>
+    void AdvanceToNextTile(TilingIteratorType* iterator);
+    template <typename TilingIteratorType>
+    bool GetFirstTileAndCheckIfValid(TilingIteratorType* iterator);
+
+    Tile* tile_;
+    PictureLayerTiling* tiling_;
+    TilingData* tiling_data_;
+  };
+
+  // Iterates over visible rect only, left to right top to bottom order.
+  class VisibleTilingIterator : public OnePriorityRectIterator {
+   public:
+    VisibleTilingIterator() = default;
+    VisibleTilingIterator(PictureLayerTiling* tiling, TilingData* tiling_data);
+
+    VisibleTilingIterator& operator++();
+
+   private:
+    TilingData::Iterator iterator_;
+  };
+
+  // Iterates over skewport only, spiral around the visible rect.
+  class SkewportTilingIterator : public OnePriorityRectIterator {
+   public:
+    SkewportTilingIterator() = default;
+    SkewportTilingIterator(PictureLayerTiling* tiling, TilingData* tiling_data);
+
+    SkewportTilingIterator& operator++();
+
+   private:
+    TilingData::SpiralDifferenceIterator iterator_;
+  };
+
+  // Iterates over soon border only, spiral around the visible rect.
+  class SoonBorderTilingIterator : public OnePriorityRectIterator {
+   public:
+    SoonBorderTilingIterator() = default;
+    SoonBorderTilingIterator(PictureLayerTiling* tiling,
+                             TilingData* tiling_data);
+
+    SoonBorderTilingIterator& operator++();
+
+   private:
+    TilingData::SpiralDifferenceIterator iterator_;
+  };
+
+  // Iterates over eventually rect only, spiral around the soon rect.
+  class EventuallyTilingIterator : public OnePriorityRectIterator {
+   public:
+    EventuallyTilingIterator() = default;
+    EventuallyTilingIterator(PictureLayerTiling* tiling,
+                             TilingData* tiling_data);
+
+    EventuallyTilingIterator& operator++();
+
+   private:
+    TilingData::SpiralDifferenceIterator iterator_;
+  };
+
+  // Iterates over all of the above phases in the following order: visible,
+  // skewport, soon border, eventually.
   class TilingIterator {
    public:
     TilingIterator();
     explicit TilingIterator(PictureLayerTiling* tiling,
                             TilingData* tiling_data);
-    ~TilingIterator();
+    ~TilingIterator() = default;
 
     bool done() const { return current_tile_ == nullptr; }
     const Tile* operator*() const { return current_tile_; }
     Tile* operator*() { return current_tile_; }
     TilePriority::PriorityBin type() const {
       switch (phase_) {
         case VISIBLE_RECT:
           return TilePriority::NOW;
         case SKEWPORT_RECT:
         case SOON_BORDER_RECT:
           return TilePriority::SOON;
         case EVENTUALLY_RECT:
           return TilePriority::EVENTUALLY;
       }
       NOTREACHED();
       return TilePriority::EVENTUALLY;
     }
 
     TilingIterator& operator++();
 
    private:
     enum Phase {
       VISIBLE_RECT,
       SKEWPORT_RECT,
       SOON_BORDER_RECT,
       EVENTUALLY_RECT
     };
 
     void AdvancePhase();
-    bool TileNeedsRaster(Tile* tile) const {
-      return tile->NeedsRaster() && !tiling_->IsTileOccluded(tile);
-    }
 
     PictureLayerTiling* tiling_;
     TilingData* tiling_data_;
 
     Phase phase_;
 
     Tile* current_tile_;
-    TilingData::Iterator visible_iterator_;
-    TilingData::SpiralDifferenceIterator spiral_iterator_;
+    VisibleTilingIterator visible_iterator_;
+    SkewportTilingIterator skewport_iterator_;
+    SoonBorderTilingIterator soon_border_iterator_;
+    EventuallyTilingIterator eventually_iterator_;
   };
 
   enum IteratorType { LOW_RES, HIGH_RES, NUM_ITERATORS };
 
   void AdvanceToNextStage();
 
   PictureLayerTilingSet* tiling_set_;
 
   struct IterationStage {
     IteratorType iterator_type;
     TilePriority::PriorityBin tile_type;
   };
 
   size_t current_stage_;
 
   // One low res stage, and three high res stages.
   IterationStage stages_[4];
   TilingIterator iterators_[NUM_ITERATORS];
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_TILING_SET_RASTER_QUEUE_ALL_H_