Compile print_preview, part 2: reduce down to 260 errors

chrome/browser/resources/print_preview/component.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.
 
 cr.define('print_preview', function() {
   'use strict';
 
   /**
    * Class that represents a UI component.
    * @constructor
@@ skipping 13 matching lines @@
 
     /**
      * Component's event tracker.
      * @type {EventTracker}
      * @private
      */
      this.tracker_ = new EventTracker();
 
     /**
      * Child components of the component.
-     * @type {Array.<print_preview.Component>}
+     * @type {Array.<!print_preview.Component>}
      * @private
      */
     this.children_ = [];
   };
 
   Component.prototype = {
     __proto__: cr.EventTarget.prototype,
 
     /** Gets the component's element. */
     getElement: function() {
@@ skipping 67 matching lines @@
      * @param {Element} element Element to decorate.
      */
     decorate: function(element) {
       assert(!this.isInDocument, 'Component is already in the document');
       this.setElementInternal(element);
       this.decorateInternal();
       this.enterDocument();
     },
 
     /**
-     * @param {print_preview.Component} child Component to add as a child of
+     * @param {!print_preview.Component} child Component to add as a child of
      *     this component.
      */
     addChild: function(child) {
       this.children_.push(child);
     },
 
     /**
      * @param {!print_preview.Component} child Component to remove from this
      *     component's children.
      */
@@ skipping 14 matching lines @@
     removeChildren: function() {
       while (this.children_.length > 0) {
         this.removeChild(this.children_[0]);
       }
     },
 
     /**
      * @param {string} query Selector query to select an element starting from
      *     the component's root element using a depth first search for the first
      *     element that matches the query.
-     * @return {HTMLElement} Element selected by the given query.
+     * @return {!HTMLElement} Element selected by the given query.

[Aleksey Shlyapnikov, 2014/09/19 18:54:42]

Why? This is a generic function and it's not guaranteed that the element we are
looking for is there.

[Vitaly Pavlenko, 2014/09/19 20:33:09]

I tried to add this assert, compile the browser and play around with
print_preview. I haven't found any failures on this assert.

Do you think that instead I should add assert() around all calls to
getChildElement()?

[Aleksey Shlyapnikov, 2014/09/19 20:48:59]

So with no assert and @return {HTMLElement} declaration Closure compiler
complains on every getChildElement's call site?

Can you leave a TODO here (on my name) to check all call sites and rename this
function to something like getRequiredChildElement?

[Vitaly Pavlenko, 2014/09/19 21:12:53]

Yes, without this assert you get 40 errors like this:
##
/usr/local/google/home/vitalyp/src/chrome/browser/resources/print_preview/search/destination_search.js:441:
ERROR - actual parameter 1 of setIsVisible does not match formal parameter
## found   : (HTMLElement|null)
## required: HTMLElement
##       setIsVisible(this.getChildElement('.cloud-list'), loggedIn);
##                    ^

TODO is inserted.

      */
     getChildElement: function(query) {
-      return this.element_.querySelector(query);
+      return assert(this.element_.querySelector(query));
     },
 
     /**
      * Sets the component's element.
      * @param {Element} element HTML element to set as the component's element.
      * @protected
      */
     setElementInternal: function(element) {
       this.element_ = element;
     },
@@ skipping 22 matching lines @@
         setIsVisible(el, true);
       }
       return el;
     }
   };
 
   return {
     Component: Component
   };
 });