[Chromoting] Fix jscompiler warnings in client_plugin_async.js

BUG=None
TEST=jscompiler reports no warnings.


Review URL: https://chromiumcodereview.appspot.com/10796097

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@148004 0039d316-1c4b-4281-b951-d872f2087c98

remoting/webapp/client_plugin_async.js

@@ -203,7 +203,8 @@ remoting.ClientPluginAsync.prototype.handleMessage_ = function(messageStr) {
       console.error('Received incorrect onConnectionReady message.');
       return;
     }
-    this.onConnectionReadyHandler(message.data['ready']);
+    var ready = /** @type {boolean} */ message.data['ready'];
+    this.onConnectionReadyHandler(ready);
   }
 }