Add tracing for DescheduleUntilFinishedCHROMIUM.

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 c765d22cd13c602eaac3d034b98ed67671cb0103..d3cc79ac52f9d9b492682a0daca8e9c9bbaf6ad6 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -13796,6 +13796,8 @@ error::Error GLES2DecoderImpl::HandleDescheduleUntilFinishedCHROMIUM(
     return error::kNoError;
   }
 
+  TRACE_EVENT_ASYNC_BEGIN0("cc", "GLES2DecoderImpl::DescheduleUntilFinished",
+                           this);
   deschedule_until_finished_callback_.Run();
   return error::kDeferLaterCommands;
 }
@@ -13933,6 +13935,8 @@ void GLES2DecoderImpl::ProcessDescheduleUntilFinished() {
   if (!deschedule_until_finished_fence_->HasCompleted())
     return;
 
+  TRACE_EVENT_ASYNC_END0("cc", "GLES2DecoderImpl::DescheduleUntilFinished",
+                         this);
   deschedule_until_finished_fence_.reset();
   reschedule_after_finished_callback_.Run();
 }