Make downloads not prevent tabs from closing....

chrome/browser/renderer_host/render_view_host.h

Index: chrome/browser/renderer_host/render_view_host.h
===================================================================
--- chrome/browser/renderer_host/render_view_host.h	(revision 21534)
+++ chrome/browser/renderer_host/render_view_host.h	(working copy)
@@ -151,7 +151,11 @@
   // Causes the renderer to invoke the onbeforeunload event handler.  The
   // result will be returned via ViewMsg_ShouldClose. See also ClosePage which
   // will fire the PageUnload event.
-  void FirePageBeforeUnload();
+  //
+  // Set bool for_cross_site_transition when this close is just for the current
+  // RenderView in the case of a cross-site transition. False means we're
+  // closing the entire tab.
+  void FirePageBeforeUnload(bool for_cross_site_transition);
 
   // Causes the renderer to close the current page, including running its
   // onunload event handler.  A ClosePage_ACK message will be sent to the
@@ -619,8 +623,17 @@
   // must return to the renderer to unblock it.
   IPC::Message* run_modal_reply_msg_;
 
+  // Set to true when there is a pending ViewMsg_ShouldClose message pending.
+  // This ensures we don't spam the renderer many times to close. When true,
+  // the value of unload_ack_is_for_cross_site_transition_ indicates which type
+  // of unload this is for.
   bool is_waiting_for_unload_ack_;
 
+  // Valid only when is_waiting_for_unload_ack_ is true, this tells us if the
+  // unload request is for closing the entire tab ( = false), or only this
+  // RenderViewHost in the case of a cross-site transition ( = true).
+  bool unload_ack_is_for_cross_site_transition_;
+
   bool are_javascript_messages_suppressed_;
 
   // True if the render view can be shut down suddenly.