Clean up examples directory

sky/examples/fps-counter.sky

-#!mojo mojo:sky_viewer
-<!--
-// Copyright 2015 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.
--->
-<import src="/sky/framework/sky-element/sky-element.sky" as="SkyElement" />
-
-<sky-element name="fps-counter" attributes="showHistory:boolean">
-<template>
-  <template if="{{ showHistory }}">
-    <template repeat="{{ deltas }}">
-      <div>{{ roundedValue }} ms</div>
-    </template>
-    <div>max = {{ max }} ms</div>
-  </template>
-  <div>fps = {{ frameRate }} Hz</div>
-</template>
-<script>
-const kMaxDeltaLength = 10;
-
-class Delta {
-  constructor(value) {
-    this.value = value;
-    this.roundedValue = value.toFixed(2);
-    Object.preventExtensions(this);
-  }
-}
-
-module.exports = class extends SkyElement {
-  created() {
-    this.frameRate = "...";
-    this.max = 0;
-    this.sum = 0;
-    this.lastTimeStamp = 0;
-    this.rafId = 0;
-    this.deltas = [];
-    for (var i = 0; i < kMaxDeltaLength; ++i)
-      this.deltas[i] = new Delta(0);
-  }
-  attached() {
-    this.scheduleTick();
-  }
-  detached() {
-    cancelAnimationFrame(this.rafId);
-    this.rafId = 0;
-  }
-  scheduleTick() {
-    this.rafId = requestAnimationFrame(this.tick.bind(this));
-  }
-  tick(timeStamp) {
-    this.scheduleTick();
-    var lastTimeStamp = this.lastTimeStamp;
-    this.lastTimeStamp = timeStamp;
-    if (!lastTimeStamp)
-      return;
-    var delta = new Delta(timeStamp - lastTimeStamp);
-    var removedDelta = this.deltas.shift();
-    this.deltas.push(delta);
-    this.sum -= removedDelta.value;
-    this.sum += delta.value;
-    var avg = this.sum / this.deltas.length;
-    this.frameRate = (1000 / avg).toFixed(2);
-    this.max = Math.max(delta.value, this.max).toFixed(2);
-  }
-}.register();
-</script>
-</sky-element>