Prevent modal dialogs when preparing to swap out.

content/renderer/render_view_impl.h

Index: content/renderer/render_view_impl.h
diff --git a/content/renderer/render_view_impl.h b/content/renderer/render_view_impl.h
index d42efa5558362aa1d3933125e67f446dbe30fdbd..f67e8d2ddc96f76eb93beb72d3b0fc4de6ef9620 100644
--- a/content/renderer/render_view_impl.h
+++ b/content/renderer/render_view_impl.h
@@ -1008,6 +1008,7 @@ class CONTENT_EXPORT RenderViewImpl
   void OnShouldClose();
   void OnStop();
   void OnStopFinding(StopFindAction action);
+  void OnSuppressDialogsUntilSwapOut();
   void OnSwapOut();
   void OnThemeChanged();
   void OnUpdateTargetURLAck();
@@ -1250,6 +1251,11 @@ class CONTENT_EXPORT RenderViewImpl
   // decidePolicyForNavigation for details.
   bool opener_suppressed_;
 
+  // Whether we must stop creating nested message loops for modal dialogs until
+  // OnSwapOut is called.  This is necessary because modal dialogs have a
+  // PageGroupLoadDeferrer on the stack that interferes with swapping out.
+  bool suppress_dialogs_until_swap_out_;
+
   // Holds state pertaining to a navigation that we initiated.  This is held by
   // the WebDataSource::ExtraData attribute.  We use pending_navigation_state_
   // as a temporary holder for the state until the WebDataSource corresponding