Change trace category to "gpu".

Bug: 874797
Change-Id: Iced662e0de18687740b1ad374f5743ae01916ef6
Reviewed-on: https://chromium-review.googlesource.com/c/1340361Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: kylechar <kylechar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608929}

services/ws/public/cpp/gpu/gpu.cc

@@ -345,7 +345,7 @@ void Gpu::EstablishGpuChannel(gpu::GpuChannelEstablishedCallback callback) {
 }
 
 scoped_refptr<gpu::GpuChannelHost> Gpu::EstablishGpuChannelSync() {
-  TRACE_EVENT0("mus", "Gpu::EstablishGpuChannelSync");
+  TRACE_EVENT0("gpu", "Gpu::EstablishGpuChannelSync");
   DCHECK(main_task_runner_->BelongsToCurrentThread());
 
   scoped_refptr<gpu::GpuChannelHost> channel = GetGpuChannel();