Added telemetry pages for the canvas element.

tools/perf/page_sets/tough_canvas_cases/rendering_throughput/canvas_arcs.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.
 // This code in inspired by the canvas arcs test on the animometer
 // benchmark (https://pr.gg/animometer/developer.html).
 // Javascript code: https://pr.gg/animometer/tests/master/resources/canvas-tests.js
 
 function CanvasArc() {
   var x;
   var y;
@@ skipping 26 matching lines @@
 
     var colors = ["#101010", "#808080", "#c0c0c0",
                   "#e01040", "#10c030", "#e05010"];
     this.color = colors[Math.floor(Math.random() * colors.length)];
 
     this.is_stroke = (Math.floor(Math.random() * 3) == 0);
 
     this.counterclockwise = (Math.floor(Math.random() * 2) == 0);
 
     this.arc_speed = (Math.random() - 0.5) * Math.PI / 10;
+
     this.start_angle = Math.random() * 2 * Math.PI;
     this.end_angle = Math.random() * 2 * Math.PI;
   }
 
   this.draw = function(context) {
     this.start_angle += this.arc_speed;
     this.end_angle += this.arc_speed / 2;
 
     // draw the canvas arc on the given context
     if (this.is_stroke) {
@@ skipping 39 matching lines @@
     // draw all initialized_arcs on the context
     for(var i = 0; i < initialized_arcs.length; i++) {
       initialized_arcs[i].draw(context);
     }
   };
 
   return arcs;
 })();