CC: Add 'cc-benchmark' traces for minimal tracing in benchmarks.

cc/output/software_renderer.cc

 // Copyright 2012 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/output/software_renderer.h"
 
 #include "base/debug/trace_event.h"
 #include "cc/base/math_util.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/output/compositor_frame_ack.h"
@@ skipping 133 matching lines @@
   TRACE_EVENT0("cc", "SoftwareRenderer::FinishDrawingFrame");
   current_framebuffer_lock_.reset();
   current_canvas_ = NULL;
   root_canvas_ = NULL;
 
   current_frame_data_.reset(new SoftwareFrameData);
   output_device_->EndPaint(current_frame_data_.get());
 }
 
 void SoftwareRenderer::SwapBuffers(const CompositorFrameMetadata& metadata) {
+  TRACE_EVENT0("cc,benchmark", "SoftwareRenderer::SwapBuffers");
   CompositorFrame compositor_frame;
   compositor_frame.metadata = metadata;
   compositor_frame.software_frame_data = current_frame_data_.Pass();
   output_surface_->SwapBuffers(&compositor_frame);
 }
 
 void SoftwareRenderer::ReceiveSwapBuffersAck(const CompositorFrameAck& ack) {
   output_device_->ReclaimSoftwareFrame(ack.last_software_frame_id);
 }
 
@@ skipping 494 matching lines @@
     return;
   visible_ = visible;
 
   if (visible_)
     EnsureBackbuffer();
   else
     DiscardBackbuffer();
 }
 
 }  // namespace cc