gpu: Fix some context lost marking glitches+leaks and add UMA stats

content/browser/compositor/gpu_process_transport_factory.cc

Index: content/browser/compositor/gpu_process_transport_factory.cc
diff --git a/content/browser/compositor/gpu_process_transport_factory.cc b/content/browser/compositor/gpu_process_transport_factory.cc
index eff234961050493e94e65506f08e83249b5cd4e2..efed67472cd162309c2124c02bc6134f8942eb3a 100644
--- a/content/browser/compositor/gpu_process_transport_factory.cc
+++ b/content/browser/compositor/gpu_process_transport_factory.cc
@@ -256,7 +256,7 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
       context_provider = ContextProviderCommandBuffer::Create(
           GpuProcessTransportFactory::CreateContextCommon(gpu_channel_host,
                                                           data->surface_id),
-          "Compositor");
+          BROWSER_COMPOSITOR_ONSCREEN_CONTEXT);
       if (context_provider && !context_provider->BindToCurrentThread())
         context_provider = nullptr;
     }
@@ -503,7 +503,7 @@ GpuProcessTransportFactory::SharedMainThreadContextProvider() {
   // context so that skia and gl_helper don't step on each other.
   shared_main_thread_contexts_ = ContextProviderCommandBuffer::Create(
       GpuProcessTransportFactory::CreateOffscreenCommandBufferContext(),
-      "Offscreen-MainThread");
+      BROWSER_OFFSCREEN_MAINTHREAD_CONTEXT);
 
   if (shared_main_thread_contexts_.get()) {
     shared_main_thread_contexts_->SetLostContextCallback(