Add fixed raster scale use counter histograms.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 97852176f80da1697da3ce3e18ad66f2df08d3a9..0ee840ffa4081ce8a994d67bd54ddb3d452370d8 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -241,7 +241,8 @@ LayerTreeHostImpl::LayerTreeHostImpl(
       id_(id),
       requires_high_res_to_draw_(false),
       is_likely_to_require_a_draw_(false),
-      mutator_(nullptr) {
+      mutator_(nullptr),
+      has_fixed_raster_scale_blurry_content_(false) {
   animation_host_ = AnimationHost::Create(ThreadInstance::IMPL);
   animation_host_->SetMutatorHostClient(this);
   animation_host_->SetSupportsScrollAnimations(SupportsImplScrolling());
@@ -354,6 +355,9 @@ void LayerTreeHostImpl::CommitComplete() {
   UpdateTreeResourcesForGpuRasterizationIfNeeded();
   sync_tree()->set_needs_update_draw_properties();
 
+  // Advance the attempted scale change history before updaring draw properties.

[danakj, 2016/05/10 22:05:30]

updating

[vmpstr, 2016/05/13 00:13:34]

Done.

+  fixed_raster_scale_attempted_scale_change_history_ <<= 1;
+
   // We need an update immediately post-commit to have the opportunity to create
   // tilings.  Because invalidations may be coming from the main thread, it's
   // safe to do an update for lcd text at this point and see if lcd text needs
@@ -3968,4 +3972,14 @@ bool LayerTreeHostImpl::CommitToActiveTree() const {
   return !task_runner_provider_->HasImplThread();
 }
 
+bool LayerTreeHostImpl::HasFixedRasterScalePotentialPerformanceRegression()
+    const {
+  return fixed_raster_scale_attempted_scale_change_history_.count() >=
+         kFixedRasterScaleAttemptedScaleChangeThreshold;
+}
+
+void LayerTreeHostImpl::SetFixedRasterScaleAttemptedToChangeScale() {
+  fixed_raster_scale_attempted_scale_change_history_.set(0);
+}
+
 }  // namespace cc