cc: Avoid expensive RenderingStats collection.

cc/raster_worker_pool.cc

Index: cc/raster_worker_pool.cc
diff --git a/cc/raster_worker_pool.cc b/cc/raster_worker_pool.cc
index 8eb92c209da3d368877d8bd47222ebf6c7b56948..51101efae17dddc87c82d5ed623f55ca6d0e4e5d 100644
--- a/cc/raster_worker_pool.cc
+++ b/cc/raster_worker_pool.cc
@@ -40,11 +40,17 @@ void RunRasterTask(PicturePileImpl* picture_pile,
 
 void RunImageDecodeTask(skia::LazyPixelRef* pixel_ref, RenderingStats* stats) {
   TRACE_EVENT0("cc", "RunImageDecodeTask");
-  base::TimeTicks decode_begin_time = base::TimeTicks::Now();
+  base::TimeTicks decode_begin_time;
+  if (stats)
+    decode_begin_time = base::TimeTicks::Now();
+
   pixel_ref->Decode();
-  stats->totalDeferredImageDecodeCount++;
-  stats->totalDeferredImageDecodeTime +=
-      base::TimeTicks::Now() - decode_begin_time;
+
+  if (stats) {
+    stats->totalDeferredImageDecodeCount++;
+    stats->totalDeferredImageDecodeTime +=
+        base::TimeTicks::Now() - decode_begin_time;
+  }
 }
 
 const char* kRasterThreadNamePrefix = "CompositorRaster";
@@ -90,9 +96,11 @@ void RasterWorkerPool::Thread::Init() {
 #endif
 }
 
-RasterWorkerPool::RasterWorkerPool(size_t num_raster_threads)
+RasterWorkerPool::RasterWorkerPool(
+    size_t num_raster_threads, bool record_rendering_stats)
     : is_running_(false),
-      raster_threads_need_sorting_(false) {
+      raster_threads_need_sorting_(false),
+      record_rendering_stats_(record_rendering_stats) {
   const std::string thread_name_prefix = kRasterThreadNamePrefix;
   while (raster_threads_.size() < num_raster_threads) {
     int thread_number = raster_threads_.size() + 1;
@@ -158,7 +166,7 @@ void RasterWorkerPool::PostRasterTaskAndReply(PicturePileImpl* picture_pile,
                  buffer,
                  rect,
                  contents_scale,
-                 &task->rendering_stats_),
+                 record_rendering_stats_ ? &task->rendering_stats_ : NULL),
       base::Bind(&RasterWorkerPool::OnRasterTaskCompleted,
                  base::Unretained(this),
                  base::Unretained(task),
@@ -174,7 +182,8 @@ void RasterWorkerPool::PostImageDecodeTaskAndReply(
 
   task->thread_->message_loop_proxy()->PostTaskAndReply(
       FROM_HERE,
-      base::Bind(&RunImageDecodeTask, pixel_ref, &task->rendering_stats_),
+      base::Bind(&RunImageDecodeTask, pixel_ref,
+                 record_rendering_stats_ ? &task->rendering_stats_ : NULL),
       base::Bind(&RasterWorkerPool::OnTaskCompleted,
                  base::Unretained(this),
                  base::Unretained(task),
@@ -182,6 +191,7 @@ void RasterWorkerPool::PostImageDecodeTaskAndReply(
 }
 
 void RasterWorkerPool::GetRenderingStats(RenderingStats* stats) {
+  DCHECK(record_rendering_stats_);
   stats->totalRasterizeTime = base::TimeDelta();
   stats->totalPixelsRasterized = 0;
   stats->totalDeferredImageDecodeCount = 0;