gpu: Completely remove GpuProcessHostUIShim.

ui/ozone/public/gpu_platform_support_host.cc

Index: ui/ozone/public/gpu_platform_support_host.cc
diff --git a/ui/ozone/public/gpu_platform_support_host.cc b/ui/ozone/public/gpu_platform_support_host.cc
index 51303018d37f54cf3aeb65991db5064c5452fbc5..2931561d53aac8aae3b317eb6cf742cd0e5dac4d 100644
--- a/ui/ozone/public/gpu_platform_support_host.cc
+++ b/ui/ozone/public/gpu_platform_support_host.cc
@@ -20,9 +20,8 @@ class StubGpuPlatformSupportHost : public GpuPlatformSupportHost {
       scoped_refptr<base::SingleThreadTaskRunner> send_runner,
       const base::Callback<void(IPC::Message*)>& send_callback) override {}
 
-  void OnChannelEstablished() override {}
-
   void OnChannelDestroyed(int host_id) override {}
+  void BindToCurrentThread() override {}
   bool OnMessageReceived(const IPC::Message&) override { return false; }
 };