<webview>: Change how plugin load works inside guests.

chrome/renderer/resources/extensions/web_view_experimental.js

 // Copyright 2013 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.
 
 // Shim extension to provide permission request API (and possibly other future
 // experimental APIs) for <webview> tag.
 // See web_view.js for details.
 //
 // We want to control the permission API feature in <webview> separately from
 // the <webview> feature itself. <webview> is available in stable channel, but
@@ skipping 100 matching lines @@
     WebView.setPermission(self.instanceId_, requestId, false, '');
     showWarningMessage(event.messageType);
   }
 };
 
 /** @private */
 WebViewInternal.prototype.maybeGetExperimentalEvents_ = function() {
   return WEB_VIEW_EXPERIMENTAL_EVENTS;
 };
 
+WebViewInternal.prototype.maybeGetExperimentalPermissions_ = function() {
+  return ['loadplugin'];
+};
+
 /** @private */
 WebViewInternal.prototype.clearData_ = function(var_args) {
   if (!this.instanceId_) {
     return;
   }
   var args = $Array.concat([this.instanceId_], $Array.slice(arguments));
   $Function.apply(WebView.clearData, null, args);
 };
 
 /** @private */
@@ skipping 29 matching lines @@
   };
 
   proto.isUserAgentOverridden = function() {
     return this.internal_(secret).isUserAgentOverridden_();
   };
 
   proto.setUserAgentOverride = function(userAgentOverride) {
     this.internal_(secret).setUserAgentOverride_(userAgentOverride);
   };
 };