Fix a Closure Compiler error.

BUG=none

Review-Url: https://codereview.chromium.org/2342203003
Cr-Commit-Position: refs/heads/master@{#419164}

ui/file_manager/gallery/js/image_editor/image_resize.js

@@ -36,6 +36,9 @@ ImageEditor.Mode.Resize = function() {
   /** @private {HTMLElement} */
   this.heightInputElement_ = null;
 
+  /** @private {HTMLElement} */
+  this.lockIcon_ = null;
+
   /** @private {number} */
   this.ratio_ = 0;