Add fixed raster scale use counter histograms.

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 935f4f01a92a60492d2c87cea6345e3e28ab10c3..b06df12866e6406baea07c10732efa13b5899695 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -7,6 +7,7 @@
 
 #include <stddef.h>
 
+#include <bitset>
 #include <memory>
 #include <set>
 #include <string>
@@ -614,6 +615,16 @@ class CC_EXPORT LayerTreeHostImpl
   void SetLayerTreeMutator(LayerTreeMutator* mutator);
   LayerTreeMutator* mutator() { return mutator_; }
 
+  void set_fixed_raster_scale_has_blurry_content() {
+    has_fixed_raster_scale_blurry_content_ = true;
+  }
+  bool has_fixed_raster_scale_blurry_content() const {
+    return has_fixed_raster_scale_blurry_content_;
+  }
+
+  bool HasFixedRasterScalePotentialPerformanceRegression() const;
+  void SetFixedRasterScaleAttemptedToChangeScale();
+
  protected:
   LayerTreeHostImpl(
       const LayerTreeSettings& settings,
@@ -641,6 +652,11 @@ class CC_EXPORT LayerTreeHostImpl
   BeginFrameTracker current_begin_frame_tracker_;
 
  private:
+  enum {
+    kFixedRasterScaleAttemptedScaleChangeThreshold = 5,
+    kFixedRasterScaleAttemptedScaleChangeHistoryCount = 10
+  };
+
   gfx::Vector2dF ScrollNodeWithViewportSpaceDelta(
       ScrollNode* scroll_node,
       const gfx::PointF& viewport_point,
@@ -844,6 +860,10 @@ class CC_EXPORT LayerTreeHostImpl
 
   LayerTreeMutator* mutator_;
 
+  bool has_fixed_raster_scale_blurry_content_;
+  std::bitset<kFixedRasterScaleAttemptedScaleChangeHistoryCount>
+      fixed_raster_scale_attempted_scale_change_history_;
+
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };