<webview>: First stab at implementing media permission request for guests.

chrome/renderer/resources/extensions/web_view_experimental_api.js

+// Copyright (c) 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
+// permission API would only be available as 'experimental'.
+
+var WebView = require('webview').WebView;
+
+/**
+ * @private
+ */
+WebView.prototype.maybeSetupPermissionEvent_ = function() {
+  this.setupEvent_('permissionrequest',
+                   ['permission', 'url'],
+                   this.preparePermissionEvent_.bind(this));
+};
+
+/**
+ * @param {Event} webViewEvt The event to be dispatched to <webview>.
+ * @param {!Object} detail The event details, originated from <object>.
+ * @private
+ */
+WebView.prototype.preparePermissionEvent_ = function(webViewEvt, detail) {
+  if (detail.permission == 'media' && detail.request_id !== undefined) {
+    // TODO(lazyboy): Also fill in webViewEvt.details (see webview specs).
+    // http://crbug.com/141197.
+    var objectNode = this.objectNode_;
+    var requestId = detail.request_id;
+    var decisionMade = false;
+    webViewEvt.allow = function() {
+      if (decisionMade) {
+        throw 'permissionrequest decision has already been made';
+      } else {
+        decisionMade = true;
+        objectNode['-internal-setMediaPermission'](requestId, true);
+      }
+    };
+    webViewEvt.deny = function() {
+      if (decisionMade) {
+        throw 'permissionrequest decision has already been made';
+      } else {
+        decisionMade = true;
+        objectNode['-internal-setMediaPermission'](requestId, false);
+      }
+    };
+  }
+};
+