Add relevant traces to measure copyFromCompositingSurface Turn-around time.

cc/output/gl_renderer.cc

 // Copyright 2010 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/gl_renderer.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 #include <string>
@@ skipping 2176 matching lines @@
     return;
 
   FlushTextureQuadCache();
   GLC(gl_, gl_->Disable(GL_SCISSOR_TEST));
   is_scissor_enabled_ = false;
 }
 
 void GLRenderer::CopyCurrentRenderPassToBitmap(
     DrawingFrame* frame,
     scoped_ptr<CopyOutputRequest> request) {
+  TRACE_EVENT0("cc", "GLRenderer::CopyCurrentRenderPassToBitmap");
   gfx::Rect copy_rect = frame->current_render_pass->output_rect;
   if (request->has_area())
     copy_rect.Intersect(request->area());
   GetFramebufferPixelsAsync(copy_rect, request.Pass());
 }
 
 void GLRenderer::ToGLMatrix(float* gl_matrix, const gfx::Transform& transform) {
   transform.matrix().asColMajorf(gl_matrix);
 }
 
@@ skipping 988 matching lines @@
     context_support_->ScheduleOverlayPlane(
         overlay.plane_z_order,
         overlay.transform,
         pending_overlay_resources_.back()->texture_id(),
         overlay.display_rect,
         overlay.uv_rect);
   }
 }
 
 }  // namespace cc