cc: add RingBuffer class for timestamp storing in FrameRateCounter

cc/layer_tree_host_impl.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 "cc/layer_tree_host_impl.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
@@ skipping 867 matching lines @@
 
 void LayerTreeHostImpl::drawLayers(FrameData& frame)
 {
     TRACE_EVENT0("cc", "LayerTreeHostImpl::drawLayers");
     DCHECK(canDraw());
     DCHECK(!frame.renderPasses.isEmpty());
 
     // 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);
 
     // Because the contents of the HUD depend on everything else in the frame, the contents
     // of its texture are updated as the last thing before the frame is drawn.
     if (m_activeTree->hud_layer())
         m_activeTree->hud_layer()->updateHudTexture(m_resourceProvider.get());
 
     m_renderer->drawFrame(frame.renderPasses);
@@ skipping 29 matching lines @@
 }
 
 const RendererCapabilities& LayerTreeHostImpl::rendererCapabilities() const
 {
     return m_renderer->capabilities();
 }
 
 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();
 }
 
 const gfx::Size& LayerTreeHostImpl::deviceViewportSize() const
 {
     return m_deviceViewportSize;
 }
 
 const LayerTreeSettings& LayerTreeHostImpl::settings() const
 {
@@ skipping 753 matching lines @@
     ScrollbarAnimationController* scrollbarController = layer->scrollbarAnimationController();
     double monotonicTime = (time - base::TimeTicks()).InSecondsF();
     if (scrollbarController && scrollbarController->animate(monotonicTime))
         m_client->setNeedsRedrawOnImplThread();
 
     for (size_t i = 0; i < layer->children().size(); ++i)
         animateScrollbarsRecursive(layer->children()[i], time);
 }
 
 }  // namespace cc