Place <webview> tag behind a flag.

chrome/renderer/extensions/dispatcher.cc

 // Copyright (c) 2012 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 "chrome/renderer/extensions/dispatcher.h"
 
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/string_piece.h"
@@ skipping 785 matching lines @@
 
       break;
     }
   }
 
   // Inject custom JS into the platform app context.
   if (IsWithinPlatformApp(frame))
     module_system->Require("platformApp");
 
   if (context_type == Feature::BLESSED_EXTENSION_CONTEXT &&
+      (CommandLine::ForCurrentProcess()->HasSwitch(switches::kEnableWebView) ||
+      (CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableBrowserPluginForAllViewTypes))) &&
       extension->HasAPIPermission(APIPermission::kWebView)) {
     module_system->Require("webview");
   }
 
   context->set_module_system(module_system.Pass());
 
   context->DispatchOnLoadEvent(
       ChromeRenderProcessObserver::is_incognito_process(),
       manifest_version);
 
@@ skipping 303 matching lines @@
   // we should abort.
   WebKit::WebFrame* frame = context->web_frame();
   ExtensionURLInfo url_info(frame->document().securityOrigin(),
       UserScriptSlave::GetDataSourceURLForFrame(frame));
   CHECK(!extensions_.IsSandboxedPage(url_info));
 
   return true;
 }
 
 }  // namespace extensions