cc: Eliminate refcount churn in prioritized tile's raster source.

This patch saves about 5% time during prepare tiles by eliminating
unnecessary refcount churn when copying prioritized tiles around in
the raster tile priority queues.

R=ericrk
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review-Url: https://codereview.chromium.org/2150473003
Cr-Commit-Position: refs/heads/master@{#405613}

cc/tiles/picture_layer_tiling.cc

@@ -778,7 +778,7 @@ PrioritizedTile PictureLayerTiling::MakePrioritizedTile(
                                    1.f / tile->contents_scale())
              .ToString();
 
-  return PrioritizedTile(tile, raster_source(),
+  return PrioritizedTile(tile, this,
                          ComputePriorityForTile(tile, priority_rect_type),
                          IsTileOccluded(tile));
 }

cc/tiles/prioritized_tile.cc

@@ -9,25 +9,19 @@
 
 namespace cc {
 
-PrioritizedTile::PrioritizedTile() : tile_(nullptr), is_occluded_(false) {}
+PrioritizedTile::PrioritizedTile() = default;
 
 PrioritizedTile::PrioritizedTile(Tile* tile,
-                                 scoped_refptr<RasterSource> raster_source,
+                                 const PictureLayerTiling* source_tiling,
                                  const TilePriority priority,
                                  bool is_occluded)
     : tile_(tile),
-      raster_source_(std::move(raster_source)),
+      source_tiling_(source_tiling),
       priority_(priority),
       is_occluded_(is_occluded) {}
 
-PrioritizedTile::PrioritizedTile(const PrioritizedTile& other) = default;
-PrioritizedTile::PrioritizedTile(PrioritizedTile&& other) = default;
 PrioritizedTile::~PrioritizedTile() = default;
 
-PrioritizedTile& PrioritizedTile::operator=(const PrioritizedTile& other) =
-    default;
-PrioritizedTile& PrioritizedTile::operator=(PrioritizedTile&& other) = default;
-
 void PrioritizedTile::AsValueInto(base::trace_event::TracedValue* value) const {
   tile_->AsValueInto(value);
 

cc/tiles/prioritized_tile.h

@@ -7,6 +7,7 @@
 
 #include "cc/base/cc_export.h"
 #include "cc/playback/raster_source.h"
+#include "cc/tiles/picture_layer_tiling.h"
 #include "cc/tiles/tile.h"
 #include "cc/tiles/tile_priority.h"
 
@@ -19,16 +20,15 @@ class CC_EXPORT PrioritizedTile {
   // This class is constructed and returned by a |PictureLayerTiling|, and
   // represents a tile and its priority.
   PrioritizedTile();
-  PrioritizedTile(const PrioritizedTile& other);
-  PrioritizedTile(PrioritizedTile&& other);
+  PrioritizedTile(Tile* tile,
+                  const PictureLayerTiling* source_tiling,
+                  const TilePriority priority,
+                  bool is_occluded);
   ~PrioritizedTile();
 
-  PrioritizedTile& operator=(const PrioritizedTile& other);
-  PrioritizedTile& operator=(PrioritizedTile&& other);
-
   Tile* tile() const { return tile_; }
   const scoped_refptr<RasterSource>& raster_source() const {
-    return raster_source_;
+    return source_tiling_->raster_source();
   }
   const TilePriority& priority() const { return priority_; }
   bool is_occluded() const { return is_occluded_; }
@@ -36,17 +36,10 @@ class CC_EXPORT PrioritizedTile {
   void AsValueInto(base::trace_event::TracedValue* value) const;
 
  private:
-  friend class PictureLayerTiling;
-
-  PrioritizedTile(Tile* tile,
-                  scoped_refptr<RasterSource> raster_source,
-                  const TilePriority priority,
-                  bool is_occluded);
-
-  Tile* tile_;
-  scoped_refptr<RasterSource> raster_source_;
+  Tile* tile_ = nullptr;
+  const PictureLayerTiling* source_tiling_ = nullptr;
   TilePriority priority_;
-  bool is_occluded_;
+  bool is_occluded_ = false;
 };
 
 }  // namespace cc