Revert of gpu: Completely remove GpuProcessHostUIShim.

ui/ozone/public/ozone_gpu_test_helper.cc

Index: ui/ozone/public/ozone_gpu_test_helper.cc
diff --git a/ui/ozone/public/ozone_gpu_test_helper.cc b/ui/ozone/public/ozone_gpu_test_helper.cc
index 55fc4b40b2145eec0497724b2b970c4672fb13b4..a08b088404ee6999008cc784d203b37f5b811cdb 100644
--- a/ui/ozone/public/ozone_gpu_test_helper.cc
+++ b/ui/ozone/public/ozone_gpu_test_helper.cc
@@ -84,8 +84,13 @@
 
     ui::OzonePlatform::GetInstance()
         ->GetGpuPlatformSupportHost()
-        ->OnGpuProcessLaunched(kGpuProcessHostId, gpu_task_runner_,
-                               gpu_io_task_runner_, sender);
+        ->OnGpuProcessLaunched(kGpuProcessHostId, gpu_io_task_runner_, sender);
+  }
+
+  void InitOnUI() {
+    ui::OzonePlatform::GetInstance()
+        ->GetGpuPlatformSupportHost()
+        ->OnChannelEstablished();
   }
 
  private:
@@ -119,6 +124,7 @@
                             base::Unretained(fake_gpu_process_host_.get())));
   io_helper_thread_->FlushForTesting();
 
+  fake_gpu_process_host_->InitOnUI();
   return true;
 }