Add type annotations to caster.js.

ui/file_manager/video_player/js/error_util.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.
 
 /**
  * This variable is checked in SelectFileDialogExtensionBrowserTest.
  * @type {number}
  */
 window.JSErrorCount = 0;
 
 /**
  * Counts uncaught exceptions.
  */
 window.onerror = function() { window.JSErrorCount++; };
 
 /**
  * Wraps the function to use it as a callback.
  * This does:
  *  - Capture the stack trace in case of error.
  *  - Bind this object
  *
- * @param {Object} thisObject Object to be used as this.
+ * @param {Object=} opt_thisObject Object to be used as this.
  * @param {...} var_args Arguments to be bound with the wrapped function.
  * @return {function} Wrapped function.
  */
-Function.prototype.wrap = function(thisObject, var_args) {
+Function.prototype.wrap = function(opt_thisObject, var_args) {
   var func = this;
   var liveStack = (new Error('Stack trace before async call')).stack;
-  if (thisObject === undefined)
-    thisObject = null;
+  var thisObject = opt_thisObject || null;
   var boundArguments = Array.prototype.slice.call(arguments, 1);
 
   return function wrappedCallback(var_args) {
     try {
       var args = boundArguments.concat(Array.prototype.slice.call(arguments));
       return func.apply(thisObject, args);
     } catch (e) {
       // Some async function doesn't handle exception correctly. So outputting
       // the exception message and stack trace just in case.
       // The message will show twice if the caller handles exception correctly.
       console.error(e.stack);
       console.info('Exception above happened in callback.', liveStack);
 
       window.JSErrorCount++;
       throw e;
     }
   }
 };