Turn on verbose flag for compiling file_manager.

ui/file_manager/gallery/js/image_editor/image_encoder.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.
 
 /**
  * A namespace class for image encoding functions. All methods are static.
  */
 function ImageEncoder() {}
 
 /**
@@ skipping 201 matching lines @@
 /**
  * Gets mime type from metadata. It reads media.mimeType at first, and if it
  * fails, it falls back to external.contentMimeType. If both fields are
  * undefined, it means that metadata is broken. Then it throws an exception.
  *
  * @param {!MetadataItem} metadata Metadata.
  * @return {string} Mime type.
  * @private
  */
 ImageEncoder.MetadataEncoder.getMimeType_ = function(metadata) {
-  if (metadata.mediaMimeType)
-    return metadata.mediaMimeType;
-  else if (metadata.contentMimeType)
-    return metadata.contentMimeType;
-
-  assertNotReached();
+  return assert(metadata.mediaMimeType || metadata.contentMimeType);
 };
 
 /**
  * Sets an image data.
  * @param {!HTMLCanvasElement} canvas Canvas or anything with width and height
  *     properties.
  */
 ImageEncoder.MetadataEncoder.prototype.setImageData = function(canvas) {
   this.imageWidth = canvas.width;
   this.imageHeight = canvas.height;
@@ skipping 19 matching lines @@
     findInsertionRange = function(encodedImage) { return {from: 0, to: 0}; };
 
 /**
  * Returns serialized metadata ready to write to an image file.
  * The return type is optimized for passing to Blob.append.
  * @return {!ArrayBuffer} Serialized metadata.
  */
 ImageEncoder.MetadataEncoder.prototype.encode = function() {
   return new Uint8Array(0).buffer;
 };