DevTools: Remove unused variables. Disallow unused variables with eslint

third_party/WebKit/Source/devtools/front_end/layer_viewer/Layers3DView.js

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 213 matching lines @@
   }
 
   _resizeCanvas() {
     this._canvasElement.width = this._canvasElement.offsetWidth * window.devicePixelRatio;
     this._canvasElement.height = this._canvasElement.offsetHeight * window.devicePixelRatio;
   }
 
   _updateTransformAndConstraints() {
     var paddingFraction = 0.1;
     var viewport = this._layerTree.viewportSize();
-    var root = this._layerTree.root();
     var baseWidth = viewport ? viewport.width : this._dimensionsForAutoscale.width;
     var baseHeight = viewport ? viewport.height : this._dimensionsForAutoscale.height;
     var canvasWidth = this._canvasElement.width;
     var canvasHeight = this._canvasElement.height;
     var paddingX = canvasWidth * paddingFraction;
     var paddingY = canvasHeight * paddingFraction;
     var scaleX = (canvasWidth - 2 * paddingX) / baseWidth;
     var scaleY = (canvasHeight - 2 * paddingY) / baseHeight;
     var viewScale = Math.min(scaleX, scaleY);
     var minScaleConstraint =
@@ skipping 933 matching lines @@
    * @return {!Promise}
    */
   update(glContext, scale) {
     this._gl = glContext;
     this.scale = scale;
     return this.snapshot.replay(null, null, scale).then(imageURL => imageURL && UI.loadImage(imageURL)).then(image => {
       this.texture = image && LayerViewer.LayerTextureManager._createTextureForImage(glContext, image);
     });
   }
 };