ui: Cleanup class/struct forward declarations

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 0fd7778b8be9252ba4b86be1b6a8b0e8790f06e6..6309cc7952b41a47710c432bb977742588f95e78 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -208,6 +208,7 @@ class CONTENT_EXPORT RenderThreadImpl
   int PostTaskToAllWebWorkers(const base::Closure& closure) override;
   bool ResolveProxy(const GURL& url, std::string* proxy_list) override;
   base::WaitableEvent* GetShutdownEvent() override;
+  int32_t GetClientId() override;
 
   // IPC::Listener implementation via ChildThreadImpl:
   void OnAssociatedInterfaceRequest(
@@ -742,6 +743,8 @@ class CONTENT_EXPORT RenderThreadImpl
   base::CancelableClosure record_purge_suspend_metric_closure_;
   bool is_renderer_suspended_;
 
+  int32_t client_id_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderThreadImpl);
 };