Make installed_loader UMA less wasteful.

extensions/browser/extension_web_contents_observer.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/browser/extension_web_contents_observer.h"
 
 #include "content/public/browser/child_process_security_policy.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/site_instance.h"
@@ skipping 62 matching lines @@
           new ExtensionMsg_Loaded(std::vector<ExtensionMsg_Loaded_Params>(
               1, ExtensionMsg_Loaded_Params(extension))));
       render_view_host->Send(
           new ExtensionMsg_ActivateExtension(extension->id()));
       break;
 
     case Manifest::TYPE_UNKNOWN:
     case Manifest::TYPE_THEME:
     case Manifest::TYPE_SHARED_MODULE:
       break;
+
+    case Manifest::NUM_LOAD_TYPES:
+      NOTREACHED();
   }
 }
 
 void ExtensionWebContentsObserver::NotifyRenderViewType(
     content::RenderViewHost* render_view_host) {
   if (render_view_host) {
     render_view_host->Send(new ExtensionMsg_NotifyRenderViewType(
         render_view_host->GetRoutingID(), GetViewType(web_contents())));
   }
 }
@@ skipping 18 matching lines @@
   // site, so we can ignore that wrinkle here.
   const GURL& site = render_view_host->GetSiteInstance()->GetSiteURL();
 
   if (!site.SchemeIs(kExtensionScheme))
     return std::string();
 
   return site.host();
 }
 
 }  // namespace extensions