Move beforeunload hang timer duties to its own timer.

content/browser/frame_host/render_frame_host_impl.h

Index: content/browser/frame_host/render_frame_host_impl.h
diff --git a/content/browser/frame_host/render_frame_host_impl.h b/content/browser/frame_host/render_frame_host_impl.h
index 74ee70b1b2541002d192b8df3fbf34ed5a768c1a..37e0998ab57bd3c844c19e18fb7e7b6761d03b9a 100644
--- a/content/browser/frame_host/render_frame_host_impl.h
+++ b/content/browser/frame_host/render_frame_host_impl.h
@@ -38,6 +38,7 @@
 #include "content/common/image_downloader/image_downloader.mojom.h"
 #include "content/common/navigation_params.h"
 #include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/renderer_unresponsive_type.h"
 #include "content/public/common/javascript_dialog_type.h"
 #include "content/public/common/previews_state.h"
 #include "media/mojo/interfaces/interface_factory.mojom.h"
@@ -879,6 +880,9 @@ class CONTENT_EXPORT RenderFrameHostImpl
   std::unique_ptr<NavigationHandleImpl> TakeNavigationHandleForCommit(
       const FrameHostMsg_DidCommitProvisionalLoad_Params& params);
 
+  // Called by |beforeunload_timeout_| when the beforeunload timeout fires.
+  void BeforeUnloadTimeout();
+
   // For now, RenderFrameHosts indirectly keep RenderViewHosts alive via a
   // refcount that calls Shutdown when it reaches zero.  This allows each
   // RenderFrameHostManager to just care about RenderFrameHosts, while ensuring
@@ -983,6 +987,14 @@ class CONTENT_EXPORT RenderFrameHostImpl
   // PlzNavigate: all navigations require a beforeUnload ACK.
   bool unload_ack_is_for_navigation_;
 
+  // The timeout monitor that runs from when the beforeunload is started in
+  // DispatchBeforeUnload() until either the render process ACKs it with an IPC
+  // to OnBeforeUnloadACK(), or until the timeout triggers.
+  std::unique_ptr<TimeoutMonitor> beforeunload_timeout_;
+
+  // If beforeunload_timeout_ is active, the type of the timeout.
+  RendererUnresponsiveType beforeunload_timeout_type_;
+
   // Indicates whether this RenderFrameHost is in the process of loading a
   // document or not.
   bool is_loading_;