Re-fix http://crbug.com/87176, and add a test.

chrome/browser/extensions/extension_host.cc

Index: chrome/browser/extensions/extension_host.cc
diff --git a/chrome/browser/extensions/extension_host.cc b/chrome/browser/extensions/extension_host.cc
index 2894013cb3a04c4a18e97e5cfb00caa61b30c8fb..74c14f6a4ba684fd7d8d161da99378deaba7d7a8 100644
--- a/chrome/browser/extensions/extension_host.cc
+++ b/chrome/browser/extensions/extension_host.cc
@@ -162,15 +162,6 @@ ExtensionHost::~ExtensionHost() {
     UMA_HISTOGRAM_LONG_TIMES("Extensions.EventPageActiveTime",
                              since_created_.Elapsed());
   }
-  // Clear the extension's renderer process out from any WebContents
-  // that might have it in their back history.
-  // TODO(jyasskin): Remove this hack by making extension reloading
-  // wait for renderer shutdown.
-  content::NotificationService::current()->Notify(
-      content::NOTIFICATION_RENDERER_PROCESS_CLOSING,
-      content::Source<content::RenderProcessHost>(render_process_host()),
-      content::NotificationService::NoDetails());
-
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_EXTENSION_HOST_DESTROYED,
       content::Source<Profile>(profile_),