ui: Cleanup class/struct forward declarations

content/public/renderer/render_thread.h

Index: content/public/renderer/render_thread.h
diff --git a/content/public/renderer/render_thread.h b/content/public/renderer/render_thread.h
index 392429ea00e168491ab0a9964f1a2b7a5af5ab5a..86e7e9f2f9a4c6650cf73ca011dac54afb49c630 100644
--- a/content/public/renderer/render_thread.h
+++ b/content/public/renderer/render_thread.h
@@ -103,6 +103,9 @@ class CONTENT_EXPORT RenderThread : virtual public ChildThread {
 
   // Gets the shutdown event for the process.
   virtual base::WaitableEvent* GetShutdownEvent() = 0;
+
+  // Retrieve the process ID of the browser process.
+  virtual int32_t GetClientId() = 0;
 };
 
 }  // namespace content