cc: fix another data race in RenderingStatsInstrumentation.

Access to the stats was not protected by a lock. Fix by returning a copy to
the stats and locking while making the copy.

R=enne@chromium.org
BUG=370244

Review URL: https://codereview.chromium.org/289163004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271646 0039d316-1c4b-4281-b951-d872f2087c98

cc/debug/rendering_stats_instrumentation.cc

@@ -18,6 +18,18 @@ RenderingStatsInstrumentation::RenderingStatsInstrumentation()
 
 RenderingStatsInstrumentation::~RenderingStatsInstrumentation() {}
 
+MainThreadRenderingStats
+RenderingStatsInstrumentation::main_thread_rendering_stats() {
+  base::AutoLock scoped_lock(lock_);
+  return main_stats_;
+}
+
+ImplThreadRenderingStats
+RenderingStatsInstrumentation::impl_thread_rendering_stats() {
+  base::AutoLock scoped_lock(lock_);
+  return impl_stats_;
+}
+
 RenderingStats RenderingStatsInstrumentation::GetRenderingStats() {
   base::AutoLock scoped_lock(lock_);
   RenderingStats rendering_stats;

cc/debug/rendering_stats_instrumentation.h

@@ -18,20 +18,19 @@ class CC_EXPORT RenderingStatsInstrumentation {
   static scoped_ptr<RenderingStatsInstrumentation> Create();
   virtual ~RenderingStatsInstrumentation();
 
-  // Return current main thread rendering stats.
-  const MainThreadRenderingStats& main_thread_rendering_stats() {
-    return main_stats_;
-  }
-  // Return current impl thread rendering stats.
-  const ImplThreadRenderingStats& impl_thread_rendering_stats() {
-    return impl_stats_;
-  }
+  // Return copy of current main thread rendering stats.
+  MainThreadRenderingStats main_thread_rendering_stats();
+
+  // Return copy of current impl thread rendering stats.
+  ImplThreadRenderingStats impl_thread_rendering_stats();
+
   // Return the accumulated, combined rendering stats.
   RenderingStats GetRenderingStats();
 
   // Add current main thread rendering stats to accumulator and
   // clear current stats.
   void AccumulateAndClearMainThreadStats();
+
   // Add current impl thread rendering stats to accumulator and
   // clear current stats.
   void AccumulateAndClearImplThreadStats();