Fix TextInputClientMac related crashes of Fullscreen RenderWidget

content/renderer/text_input_client_observer.h

Index: content/renderer/text_input_client_observer.h
diff --git a/content/renderer/text_input_client_observer.h b/content/renderer/text_input_client_observer.h
index 6871057ba283f8d28f8a290dae6541bb2f46a4b1..4e065b1a5514bff3fce0810153ae57b7c090228d 100644
--- a/content/renderer/text_input_client_observer.h
+++ b/content/renderer/text_input_client_observer.h
@@ -36,7 +36,8 @@ class TextInputClientObserver : public IPC::Listener, public IPC::Sender {
   bool Send(IPC::Message* message) override;
 
  private:
-  // The render widget corresponding to this TextInputClientObserver.
+  // Returns the WebFrameWidget for the RenderWidget owning this observer. It
+  // returns null if the RenderWidget corresponds to a fullscreen RenderWidget.
   blink::WebFrameWidget* GetWebFrameWidget() const;
 
   blink::WebLocalFrame* GetFocusedFrame() const;