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

cc/output/delegating_renderer.cc

Index: cc/output/delegating_renderer.cc
diff --git a/cc/output/delegating_renderer.cc b/cc/output/delegating_renderer.cc
index e56d1465a1683728d6b607d68f6ca6c961754df5..292e3abb03ef97b9988207be6870456d74a45457 100644
--- a/cc/output/delegating_renderer.cc
+++ b/cc/output/delegating_renderer.cc
@@ -122,7 +122,7 @@ void DelegatingRenderer::DrawFrame(RenderPassList* render_passes_in_draw_order,
 }
 
 void DelegatingRenderer::SwapBuffers(const CompositorFrameMetadata& metadata) {
-  TRACE_EVENT0("cc", "DelegatingRenderer::SwapBuffers");
+  TRACE_EVENT0("cc,cc-benchmark", "DelegatingRenderer::SwapBuffers");
   CompositorFrame compositor_frame;
   compositor_frame.metadata = metadata;
   compositor_frame.delegated_frame_data = delegated_frame_data_.Pass();