add "did it run on GPU" check to frame_rate_tests.cc using AutomationProxy tracing feature

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index c525908a1f14913df300d49dfcacb0073f1bd710..a23c583f704bea056790996864818a97a1ef336e 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -6805,6 +6805,9 @@ error::Error GLES2DecoderImpl::HandleSwapBuffers(
     uint32 immediate_data_size, const gles2::SwapBuffers& c) {
   bool is_offscreen = !!offscreen_target_frame_buffer_.get();
   int this_frame_number = frame_number_++;
+  // This event is used by frame_rate_tests:
+  TRACE_EVENT_INSTANT1("test_frame_rate_tests", "SwapBuffers",
+                       "GLImpl", static_cast<int>(gfx::GetGLImplementation()));
   TRACE_EVENT2("gpu", "GLES2DecoderImpl::HandleSwapBuffers",
                "offscreen", is_offscreen,
                "frame", this_frame_number);