Turn on verbose flag for compiling file_manager.

ui/file_manager/gallery/js/image_editor/image_transform.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.
 
 /**
  * Crop mode.
  *
  * @extends {ImageEditor.Mode}
  * @constructor
  * @struct
@@ skipping 64 matching lines @@
 /**
  * Sets the mode up.
  * @override
  */
 ImageEditor.Mode.Crop.prototype.setUp = function() {
   ImageEditor.Mode.prototype.setUp.apply(this, arguments);
 
   var container = this.getImageView().container_;
   var doc = container.ownerDocument;
 
-  this.domOverlay_ = doc.createElement('div');
+  this.domOverlay_ = assertInstanceof(doc.createElement('div'), HTMLDivElement);

[Dan Beam, 2015/10/16 07:20:47]

why do these need to be HTMLDivElement rather than HTMLElement?  do you use
this.domOverlay_.align somewhere?

[fukino, 2015/10/19 09:55:14]

As we call createElement('div'), we expect the returned element is
HTMLDivElement. In general, should we use HTMLElement as long as we don't touch
specific properties of descendent classes.

[Dan Beam, 2015/10/20 00:33:37]

yes, i understand.  HTMLDivElement#align is the /only/ thing that <div> has that
HTMLElement doesn't.  that's why I ask.

these should all be HTMLElement.

https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

   this.domOverlay_.className = 'crop-overlay';
   container.appendChild(this.domOverlay_);
 
-  this.shadowTop_ = doc.createElement('div');
+  this.shadowTop_ = assertInstanceof(doc.createElement('div'), HTMLDivElement);
   this.shadowTop_.className = 'shadow';
   this.domOverlay_.appendChild(this.shadowTop_);
 
-  this.middleBox_ = doc.createElement('div');
+  this.middleBox_ = assertInstanceof(doc.createElement('div'), HTMLDivElement);
   this.middleBox_.className = 'middle-box';
   this.domOverlay_.appendChild(this.middleBox_);
 
-  this.shadowLeft_ = doc.createElement('div');
+  this.shadowLeft_ = assertInstanceof(doc.createElement('div'), HTMLDivElement);
   this.shadowLeft_.className = 'shadow';
   this.middleBox_.appendChild(this.shadowLeft_);
 
-  this.cropFrame_ = doc.createElement('div');
+  this.cropFrame_ = assertInstanceof(doc.createElement('div'), HTMLDivElement);
   this.cropFrame_.className = 'crop-frame';
   this.middleBox_.appendChild(this.cropFrame_);
 
-  this.shadowRight_ = doc.createElement('div');
+  this.shadowRight_ = assertInstanceof(doc.createElement('div'),
+                                       HTMLDivElement);
   this.shadowRight_.className = 'shadow';
   this.middleBox_.appendChild(this.shadowRight_);
 
-  this.shadowBottom_ = doc.createElement('div');
+  this.shadowBottom_ = assertInstanceof(doc.createElement('div'),
+                                        HTMLDivElement);
   this.shadowBottom_.className = 'shadow';
   this.domOverlay_.appendChild(this.shadowBottom_);
 
   var cropFrame = this.cropFrame_;
   function addCropFrame(className) {
     var div = doc.createElement('div');
     div.className = className;
     cropFrame.appendChild(div);
   }
 
@@ skipping 617 matching lines @@
       break;
     case 'bottom':
       this.bounds_.bottom = this.bounds_.top + newHeight;
       break;
     case 'none':
       this.bounds_.top = middle - newHeight / 2;
       this.bounds_.bottom = middle + newHeight / 2;
       break;
   }
 };