Don't crash on chrome.runtime.connect().

extensions/renderer/resources/runtime_custom_bindings.js

 // 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.
 
 // Custom binding for the runtime API.
 
 var binding = require('binding').Binding.create('runtime');
 
 var messaging = require('messaging');
 var runtimeNatives = requireNative('runtime');
@@ skipping 140 matching lines @@
     }
     return [appName];
   });
 
   apiFunctions.setHandleRequest('connect', function(targetId, connectInfo) {
     // Don't let orphaned content scripts communicate with their extension.
     // http://crbug.com/168263
     if (unloadEvent.wasDispatched)
       throw new Error('Error connecting to extension ' + targetId);
 
-    if (!targetId)
+    if (!targetId) {
+      // runtime.id is only defined inside extensions. If we're in a webpage,
+      // the best we can do at this point is to fail.
+      if (!runtime.id) {
+        throw new Error('chrome.runtime.connect() called from a webpage must ' +
+                        'specify an Extension ID (string) for its first ' +
+                        'argument');
+      }
       targetId = runtime.id;
+    }
 
     var name = '';
     if (connectInfo && connectInfo.name)
       name = connectInfo.name;
 
     var includeTlsChannelId =
       !!(connectInfo && connectInfo.includeTlsChannelId);
 
     var portId = runtimeNatives.OpenChannelToExtension(targetId, name,
                                                        includeTlsChannelId);
@@ skipping 24 matching lines @@
       var bg = runtimeNatives.GetExtensionViews(-1, 'BACKGROUND')[0] || null;
       callback(bg);
     }
   });
 
   bindDirectoryEntryCallback('getPackageDirectoryEntry', apiFunctions);
 });
 
 exports.bindDirectoryEntryCallback = bindDirectoryEntryCallback;
 exports.binding = binding.generate();