Check existence of chrome.runtime APIs using __lookupGetter__ to avoid throwing

chrome/renderer/resources/extensions/extension_custom_bindings.js

 // 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.
 
 // Custom bindings for the extension API.
 
 var extensionNatives = requireNative('extension');
 var GetExtensionViews = extensionNatives.GetExtensionViews;
 var runtimeNatives = requireNative('runtime');
 var OpenChannelToExtension = runtimeNatives.OpenChannelToExtension;
@@ skipping 61 matching lines @@
   // Alias several messaging deprecated APIs to their runtime counterparts.
   var mayNeedAlias = [
     // Types
     'Port',
     // Functions
     'connect', 'sendMessage', 'connectNative', 'sendNativeMessage',
     // Events
     'onConnect', 'onConnectExternal', 'onMessage', 'onMessageExternal'
   ];
   mayNeedAlias.forEach(function(alias) {
-    try {
-      // Deliberately accessing runtime[alias] rather than testing its
-      // existence, since accessing may throw an exception if this context
-      // doesn't have access.
-      if (chrome.runtime[alias])
-        chrome.extension[alias] = chrome.runtime[alias];
-    } catch(e) {}
+    // Checking existence isn't enough since some functions are disabled via
+    // getters that throw exceptions. Assume that any getter is such a function.
+    if (chrome.runtime.hasOwnProperty(alias) &&
+        chrome.runtime.__lookupGetter__(alias) === undefined) {
+      chrome.extension[alias] = chrome.runtime[alias];
+    }
   });
 
   apiFunctions.setUpdateArgumentsPreValidate('sendRequest',
       sendMessageUpdateArguments.bind(null, 'sendRequest'));
 
   apiFunctions.setHandleRequest('sendRequest',
                                 function(targetId, request, responseCallback) {
     if (sendRequestIsDisabled)
       throw new Error(sendRequestIsDisabled);
     var port = chrome.runtime.connect(targetId || extensionId,
                                       {name: chromeHidden.kRequestChannel});
     chromeHidden.Port.sendMessageImpl(port, request, responseCallback);
   });
 
   if (sendRequestIsDisabled) {
     chrome.extension.onRequest.addListener = function() {
       throw new Error(sendRequestIsDisabled);
     };
     if (contextType == 'BLESSED_EXTENSION') {
       chrome.extension.onRequestExternal.addListener = function() {
         throw new Error(sendRequestIsDisabled);
       };
     }
   }
 
 });