Fix DevToolsBeforeUnloadTest and BrowserCloseManagerBrowserTest.

content/public/browser/render_frame_host.h

Index: content/public/browser/render_frame_host.h
diff --git a/content/public/browser/render_frame_host.h b/content/public/browser/render_frame_host.h
index 2fcedbce3de7dda0751507525ca16611b2bc1fd5..f7d7cb1303ef94bfd5222098383cf75c99742a40 100644
--- a/content/public/browser/render_frame_host.h
+++ b/content/public/browser/render_frame_host.h
@@ -241,6 +241,11 @@ class CONTENT_EXPORT RenderFrameHost : public IPC::Listener,
   virtual service_manager::InterfaceProvider* GetJavaInterfaces() = 0;
 #endif  // OS_ANDROID
 
+  // Stops and disables the hang monitor for beforeunload. This avoids flakiness
+  // in tests that need to observe beforeunload dialogs, which could fail if the
+  // timeout skips the dialog.
+  virtual void DisableBeforeUnloadHangMonitorForTesting() = 0;
+
  private:
   // This interface should only be implemented inside content.
   friend class RenderFrameHostImpl;