cc: Avoid expensive RenderingStats collection.

cc/tile_manager.cc

Index: cc/tile_manager.cc
diff --git a/cc/tile_manager.cc b/cc/tile_manager.cc
index de7bf0d816e7929e8f8d49279bb82148879d829a..dd1cb6ad9fd3c9b273e4aa10939e3b9674c1239b 100644
--- a/cc/tile_manager.cc
+++ b/cc/tile_manager.cc
@@ -118,14 +118,17 @@ ManagedTileState::~ManagedTileState() {
 TileManager::TileManager(
     TileManagerClient* client,
     ResourceProvider* resource_provider,
-    size_t num_raster_threads)
+    size_t num_raster_threads,
+    bool record_rendering_stats)
     : client_(client),
       resource_pool_(ResourcePool::Create(resource_provider)),
-      raster_worker_pool_(RasterWorkerPool::Create(num_raster_threads)),
+      raster_worker_pool_(RasterWorkerPool::Create(
+          num_raster_threads, record_rendering_stats)),
       manage_tiles_pending_(false),
       manage_tiles_call_count_(0),
       bytes_pending_set_pixels_(0),
-      ever_exceeded_memory_budget_(false) {
+      ever_exceeded_memory_budget_(false),
+      record_rendering_stats_(record_rendering_stats) {
   bool worker_pool_is_running = raster_worker_pool_->Start();
   CHECK(worker_pool_is_running);
 
@@ -405,6 +408,7 @@ scoped_ptr<base::Value> TileManager::GetMemoryRequirementsAsValue() const {
 }
 
 void TileManager::GetRenderingStats(RenderingStats* stats) {
+  DCHECK(record_rendering_stats_);
   raster_worker_pool_->GetRenderingStats(stats);
   stats->totalDeferredImageCacheHitCount =
       rendering_stats_.totalDeferredImageCacheHitCount;
@@ -569,15 +573,19 @@ void TileManager::GatherPixelRefsForTile(Tile* tile) {
   TRACE_EVENT0("cc", "TileManager::GatherPixelRefsForTile");
   ManagedTileState& managed_state = tile->managed_state();
   if (managed_state.need_to_gather_pixel_refs) {
-    base::TimeTicks gather_begin_time = base::TimeTicks::Now();
+    base::TimeTicks gather_begin_time;
+    if (record_rendering_stats_)
+      gather_begin_time = base::TimeTicks::Now();
     tile->picture_pile()->GatherPixelRefs(
         tile->content_rect_,
         tile->contents_scale_,
         managed_state.pending_pixel_refs);
-    rendering_stats_.totalImageGatheringCount++;
-    rendering_stats_.totalImageGatheringTime +=
-        base::TimeTicks::Now() - gather_begin_time;
     managed_state.need_to_gather_pixel_refs = false;
+    if (record_rendering_stats_) {
+      rendering_stats_.totalImageGatheringCount++;
+      rendering_stats_.totalImageGatheringTime +=
+          base::TimeTicks::Now() - gather_begin_time;
+    }
   }
 }