Don't close background pages if there is a pending response (callback).

chrome/browser/renderer_host/chrome_render_message_filter.cc

Index: chrome/browser/renderer_host/chrome_render_message_filter.cc
diff --git a/chrome/browser/renderer_host/chrome_render_message_filter.cc b/chrome/browser/renderer_host/chrome_render_message_filter.cc
index 5472214c920f3919a7d4ca2237422002232889a8..9e98fddd7a1dcfbca6d075510736df7b11f07fbe 100644
--- a/chrome/browser/renderer_host/chrome_render_message_filter.cc
+++ b/chrome/browser/renderer_host/chrome_render_message_filter.cc
@@ -130,6 +130,7 @@ bool ChromeRenderMessageFilter::OnMessageReceived(const IPC::Message& message,
     IPC_MESSAGE_HANDLER(ExtensionHostMsg_RemoveListener,
                         OnExtensionRemoveListener)
     IPC_MESSAGE_HANDLER(ExtensionHostMsg_ExtensionIdle, OnExtensionIdle)
+    IPC_MESSAGE_HANDLER(ExtensionHostMsg_EventDispatch, OnEventDispatch)
     IPC_MESSAGE_HANDLER(ExtensionHostMsg_CloseChannel, OnExtensionCloseChannel)
     IPC_MESSAGE_HANDLER(ExtensionHostMsg_RequestForIOThread,
                         OnExtensionRequestForIOThread)
@@ -192,6 +193,7 @@ void ChromeRenderMessageFilter::OverrideThreadForMessage(
     case ExtensionHostMsg_AddListener::ID:
     case ExtensionHostMsg_RemoveListener::ID:
     case ExtensionHostMsg_ExtensionIdle::ID:
+    case ExtensionHostMsg_EventDispatch::ID:
     case ExtensionHostMsg_CloseChannel::ID:
     case ChromeViewHostMsg_UpdatedCacheStats::ID:
       *thread = BrowserThread::UI;
@@ -381,6 +383,12 @@ void ChromeRenderMessageFilter::OnExtensionIdle(
     profile_->GetExtensionProcessManager()->OnExtensionIdle(extension_id);
 }
 
+void ChromeRenderMessageFilter::OnEventDispatch(
+    const std::string& extension_id) {
+  if (profile_->GetExtensionEventRouter())
+    profile_->GetExtensionEventRouter()->DecrementInFlightEvents(extension_id);
+}
+
 void ChromeRenderMessageFilter::OnExtensionCloseChannel(int port_id) {
   if (!RenderProcessHost::FromID(render_process_id_))
     return;  // To guard against crash in browser_tests shutdown.