gpu: Replace GpuMsg_Finalize ipc with equivalent mojom api

content/browser/gpu/gpu_process_host.h

Index: content/browser/gpu/gpu_process_host.h
diff --git a/content/browser/gpu/gpu_process_host.h b/content/browser/gpu/gpu_process_host.h
index 167b4d223c0aec0431570e84df5291645d2d85aa..973e14e533f7760a39b505a9507d4d6d78c7479a 100644
--- a/content/browser/gpu/gpu_process_host.h
+++ b/content/browser/gpu/gpu_process_host.h
@@ -101,8 +101,9 @@ class GpuProcessHost : public BrowserChildProcessHostDelegate,
                                       IPC::Message* message);
 
   // Helper function to run a callback on the IO thread. The callback receives
-  // the appropriate GpuProcessHost instance. If |force_create| is false, and no
-  // GpuProcessHost instance exists, then the callback is never called.
+  // the appropriate GpuProcessHost instance. Note that the callback can be
+  // called with a null host (e.g. when |force_create| is false, and no
+  // GpuProcessHost instance exists).
   CONTENT_EXPORT static void CallOnIO(
       GpuProcessKind kind,
       bool force_create,
@@ -157,9 +158,6 @@ class GpuProcessHost : public BrowserChildProcessHostDelegate,
   // Forcefully terminates the GPU process.
   void ForceShutdown();
 
-  // Asks the GPU process to stop by itself.
-  void StopGpuProcess();
-
   void LoadedShader(const std::string& key, const std::string& data);
 
   ui::mojom::GpuService* gpu_service() { return gpu_service_ptr_.get(); }