Prevent modal dialogs when preparing to swap out.

content/browser/renderer_host/render_view_host_impl.h

Index: content/browser/renderer_host/render_view_host_impl.h
diff --git a/content/browser/renderer_host/render_view_host_impl.h b/content/browser/renderer_host/render_view_host_impl.h
index 0a5e307b93559b6d19afa2b87c6009108782fc6b..d21c0a662321eae68c78d8201dd9af3989158c43 100644
--- a/content/browser/renderer_host/render_view_host_impl.h
+++ b/content/browser/renderer_host/render_view_host_impl.h
@@ -289,6 +289,12 @@ class CONTENT_EXPORT RenderViewHostImpl
   // different process.
   bool is_swapped_out() const { return is_swapped_out_; }
 
+  // Tells the renderer that this RenderView will soon be swapped out, and thus
+  // not to create any new modal dialogs until it happens.  This must be done
+  // separately so that the PageGroupLoadDeferrers of any current dialogs are no
+  // longer on the stack when we attempt to swap it out.
+  void SuppressDialogsUntilSwapOut();
+
   // Tells the renderer that this RenderView is being swapped out for one in a
   // different renderer process.  It should run its unload handler and move to
   // a blank document.  The renderer should preserve the Frame object until it