Can more conveniently set easing from JS.

chrome/browser/resources/vr_shell/vr_shell_ui_api.js

 // Copyright 2016 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.
 
 var api = {};
 
 /**
  * Enumeration of scene update commands.
  * @enum {number}
  * @const
@@ skipping 315 matching lines @@
   'SCALE': 3,
   'ROTATION': 4,
   'OPACITY': 5
 };
 
 /**
  * Enumeration of easing type.
  * @enum {number}
  * @const
  */
-api.Easing = {
+api.EasingType = {
   'LINEAR': 0,
   'CUBICBEZIER': 1,
   'EASEIN': 2,
   'EASEOUT': 3
 };
 
 /**
+ * Abstract easing base class.
+ * @abstract

[cjgrant, 2017/02/16 14:51:47]

Nice!  I missed that @abstract exists.  Could you apply it to
NativeCommandHandler as well?

[tiborg, 2017/02/16 17:30:49]

Done. Also added to fill class.

+ */
+api.Easing = class {
+  constructor(type) {
+    this.type = type;
+  }
+}
+
+api.LinearEasing = class extends api.Easing {
+  constructor() {
+    super(api.EasingType.LINEAR);
+  }
+}
+
+api.CubicBezierEasing = class extends api.Easing {
+  constructor(p1x, p1y, p2x, p2y) {

[mthiesse, 2017/02/16 15:12:06]

We should provide reasonable defaults for all easing parameters. Josh originally
pushed back on even having them as part of the API and wanted us to just provide
good values natively. At least if there are defaults here he can tweak them.

[tiborg, 2017/02/16 17:30:49]

Makes sense. Done.

+    super(api.EasingType.CUBICBEZIER);
+    this.p1x = p1x;
+    this.p1y = p1y;
+    this.p2x = p2x;
+    this.p2y = p2y;
+  }
+}
+
+api.InEasing = class extends api.Easing {
+  constructor(pow) {
+    super(api.EasingType.EASEIN);
+    this.pow = pow;
+  }
+}
+
+api.OutEasing = class extends api.Easing {
+  constructor(pow) {
+    super(api.EasingType.EASEOUT);
+    this.pow = pow;
+  }
+}
+
+/**
  * Base animation class. An animation can vary only one object property.
  * @struct
  */
 api.Animation = class {
   constructor(elementId, durationMs) {
     /** @private {number} */
     this.id = -1;
     /** @private {number} */
     this.meshId = elementId;
     /** @private {number} */
     this.property = -1;
     /** @private {Object} */
     this.to = {};
     /** @private {Object} */
-    this.easing = {};
+    this.easing = new api.LinearEasing();
 
     // How many milliseconds in the future to start the animation.
     /** @private {number} */
     this.startInMillis = 0.0;
 
     // Duration of the animation (milliseconds).
     /** @private {number} */
     this.durationMillis = durationMs;
-
-    this.easing.type = api.Easing.LINEAR;
   }
 
   /**
    * Set the id of the animation.
    * @param {number} id
    */
   setId(id) {
     this.id = id;
   }
 
@@ skipping 50 matching lines @@
   }
 
   /**
    * Set the animation's final element opacity.
    * @param {number} opacity
    */
   setOpacity(opacity) {
     this.property = api.Property.OPACITY;
     this.to.x = opacity;
   }
+
+  /**
+   * Set the animation's easing.
+   * @param {api.Easing} easing
+   */
+  setEasing(easing) {
+    this.easing = easing;
+  }
 };
 
 /**
  * Abstract class handling webui command calls from native.  The UI must
  * subclass this and override the handlers.
  */
 api.NativeCommandHandler = class {
   /**
    * @param {api.Mode} mode
    */
@@ skipping 119 matching lines @@
     if ('updateTab' in dict) {
       this.onUpdateTab(dict['updateTabs']);
     }
     if ('removeTab' in dict) {
       this.onRemoveTab(dict['removeTab']);
     }
 
     this.onCommandHandlerFinished()
   }
 };