cc: add RingBuffer class for timestamp storing in FrameRateCounter

cc/layer_tree_host_impl.cc

Index: cc/layer_tree_host_impl.cc
diff --git a/cc/layer_tree_host_impl.cc b/cc/layer_tree_host_impl.cc
index 9d42698bae2a192a8e6884cd6011c818bd8040d1..5cb231184da8c4deb8682cf1e94653f166a205d8 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -885,7 +885,7 @@ void LayerTreeHostImpl::drawLayers(FrameData& frame)
     // FIXME: use the frame begin time from the overall compositor scheduler.
     // This value is currently inaccessible because it is up in Chromium's
     // RenderWidget.
-    m_fpsCounter->markBeginningOfFrame(base::TimeTicks::Now());
+    m_fpsCounter->saveTimeStamp(base::TimeTicks::Now());
 
     if (m_debugState.showHudRects())
         m_debugRectHistory->saveDebugRectsForCurrentFrame(rootLayer(), *frame.renderSurfaceLayerList, frame.occludingScreenSpaceRects, frame.nonOccludingScreenSpaceRects, m_debugState);
@@ -935,8 +935,6 @@ const RendererCapabilities& LayerTreeHostImpl::rendererCapabilities() const
 bool LayerTreeHostImpl::swapBuffers()
 {
     DCHECK(m_renderer);
-
-    m_fpsCounter->markEndOfFrame();

[egraether, 2013/01/09 02:04:04]

I found this call had no real purpose and was leading to confusion.

     return m_renderer->swapBuffers();
 }