cc: Turn overdraw metrics on only when about:tracing is recording.

cc/layer_tree_host.cc

 // Copyright 2011 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.
 
 #include "config.h"
 
 #include "cc/layer_tree_host.h"
 
 #include "Region.h"
 #include "base/debug/trace_event.h"
@@ skipping 650 matching lines @@
     }
     return needMoreUpdates;
 }
 
 bool LayerTreeHost::paintLayerContents(const LayerList& renderSurfaceLayerList, ResourceUpdateQueue& queue)
 {
     // Use FrontToBack to allow for testing occlusion and performing culling during the tree walk.
     typedef LayerIterator<Layer, LayerList, RenderSurface, LayerIteratorActions::FrontToBack> LayerIteratorType;
 
     bool needMoreUpdates = false;
-    bool recordMetricsForFrame = true; // FIXME: In the future, disable this when about:tracing is off.
+    bool recordMetricsForFrame = base::debug::TraceLog::GetInstance() && base::debug::TraceLog::GetInstance()->IsEnabled();
     OcclusionTracker occlusionTracker(m_rootLayer->renderSurface()->contentRect(), recordMetricsForFrame);
     occlusionTracker.setMinimumTrackingSize(m_settings.minimumOcclusionTrackingSize);
 
     prioritizeTextures(renderSurfaceLayerList, occlusionTracker.overdrawMetrics());
 
     LayerIteratorType end = LayerIteratorType::end(&renderSurfaceLayerList);
     for (LayerIteratorType it = LayerIteratorType::begin(&renderSurfaceLayerList); it != end; ++it) {
         occlusionTracker.enterLayer(it);
 
         if (it.representsTargetRenderSurface()) {
@@ skipping 158 matching lines @@
             else
                 layer->notifyAnimationFinished(wallClockTime.ToDoubleT());
         }
     }
 
     for (size_t childIndex = 0; childIndex < layer->children().size(); ++childIndex)
         setAnimationEventsRecursive(events, layer->children()[childIndex].get(), wallClockTime);
 }
 
 }  // namespace cc