Introduce a monotonic_clock module for Mojo.js.

mojo/apps/js/main.js

 // Copyright 2013 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.
 
 define([
     'console',
+    'monotonic_clock',
     'timer',
     'mojo/apps/js/bindings/connector',
     'mojo/apps/js/bindings/core',
     'mojo/apps/js/bindings/gl',
     'mojo/apps/js/bindings/threading',
     'mojom/native_viewport',
     'mojom/gles2',
     'mojom/shell',
 ], function(console,
+            monotonicClock,
             timer,
             connector,
             core,
             gljs,
             threading,
             nativeViewport,
             gles2,
             shell) {
 
   const VERTEX_SHADER_SOURCE = [
@@ skipping 280 matching lines @@
   NativeViewportClientImpl.prototype.onCreated = function() {
     console.log('NativeViewportClientImpl.prototype.OnCreated');
   };
   NativeViewportClientImpl.prototype.didOpen = function() {
     console.log('NativeViewportClientImpl.prototype.DidOpen');
   };
 
 
   function GLES2ClientImpl(remote) {
     this.remote_ = remote;
-    this.lastTime_ = Date.now();
+    this.lastTime_ = monotonicClock.seconds();
     this.angle_ = 45;
   }
   GLES2ClientImpl.prototype =
       Object.create(gles2.GLES2ClientStub.prototype);
 
   GLES2ClientImpl.prototype.didCreateContext = function(encoded,
                                                         width,
                                                         height) {
     this.width_ = width;
     this.height_ = height;
@@ skipping 20 matching lines @@
     this.gl_.vertexAttribPointer(this.positionLocation_, 3, this.gl_.FLOAT,
                                  false, 12, 0);
     this.gl_.enableVertexAttribArray(this.positionLocation_);
     this.gl_.uniformMatrix4fv(this.mvpLocation_, false, this.mvpMatrix_.m);
     this.gl_.drawElements(this.gl_.TRIANGLES, this.numIndices_,
                           this.gl_.UNSIGNED_SHORT, 0);
     this.gl_.swapBuffers();
   };
 
   GLES2ClientImpl.prototype.handleTimer = function() {
-    var now = Date.now();
-    var timeDelta = Date.now() - this.lastTime_;
+    var now = monotonicClock.seconds();
+    var secondsDelta = now - this.lastTime_;
     this.lastTime_ = now;
 
-    this.angle_ += this.getRotationForTimeDelgate(timeDelta);
+    this.angle_ += this.getRotationForTimeDelta(secondsDelta);
     this.angle_ = this.angle_ % 360;
 
     var aspect = this.width_ / this.height_;
 
     var perspective = new ESMatrix();
     perspective.loadIdentity();
     perspective.perspective(60, aspect, 1, 20);
 
     var modelView = new ESMatrix();
     modelView.loadIdentity();
     modelView.translate(0, 0, -2);
     modelView.rotate(this.angle_, 1, 0, 1);
 
     this.mvpMatrix_.multiply(modelView, perspective);
 
     this.drawCube();
   };
 
-  GLES2ClientImpl.prototype.getRotationForTimeDelgate = function(timeDelta) {
-    return timeDelta * .04;
+  GLES2ClientImpl.prototype.getRotationForTimeDelta = function(secondsDelta) {
+    return secondsDelta * 40;
   };
 
   GLES2ClientImpl.prototype.contextLost = function() {
     console.log('GLES2ClientImpl.prototype.contextLost');
   };
 
 
   return function(handle) {
     new connector.Connection(handle, SampleApp, shell.ShellProxy);
   };
 });