Don't leave renderer process frozen when canceling JavaScript dialogs.

content/browser/web_contents/render_view_host_manager.cc

Index: content/browser/web_contents/render_view_host_manager.cc
diff --git a/content/browser/web_contents/render_view_host_manager.cc b/content/browser/web_contents/render_view_host_manager.cc
index db8d1d0553b3a0b232d98249ae189a0522c0d695..ee5973f440197edc253823fa50a312ff2c3ebb60 100644
--- a/content/browser/web_contents/render_view_host_manager.cc
+++ b/content/browser/web_contents/render_view_host_manager.cc
@@ -387,6 +387,9 @@ void RenderViewHostManager::SwapOutOldPage() {
     return;
   DCHECK(pending_render_view_host_);
 
+  // First close any modal dialogs that would prevent us from swapping out.
+  delegate_->CancelModalDialogsForRenderManager();
+
   // Tell the old renderer it is being swapped out.  This will fire the unload
   // handler (without firing the beforeunload handler a second time).  When the
   // unload handler finishes and the navigation completes, we will send a