Mouse (#101)

This patch:
- adds Mouse class which holds mouse state and implements mouse primitives,
such as moving, button down and button up.
- implements high-level mouse api, such as `page.click` and `page.hover`.

References #40, References #89

lib/FrameManager.js

@@ -20,20 +20,23 @@ let helper = require('./helper');
 class FrameManager extends EventEmitter {
   /**
    * @param {!Connection} client
+   * @param {!Mouse} mouse
    * @return {!Promise<!FrameManager>}
    */
-  static async create(client) {
+  static async create(client, mouse) {
     let mainFramePayload = await client.send('Page.getResourceTree');
-    return new FrameManager(client, mainFramePayload.frameTree);
+    return new FrameManager(client, mainFramePayload.frameTree, mouse);
   }
 
   /**
    * @param {!Connection} client
    * @param {!Object} frameTree
+   * @param {!Mouse} mouse
    */
-  constructor(client, frameTree) {
+  constructor(client, frameTree, mouse) {
     super();
     this._client = client;
+    this._mouse = mouse;
     /** @type {!Map<string, !Frame>} */
     this._frames = new Map();
     this._mainFrame = this._addFramesRecursively(null, frameTree);
@@ -405,6 +408,39 @@ class Frame {
     return this._frameManager._evaluateOnFrame(this, expression);
   }
 
+  /**
+   * @param {string} selector
+   * @return {!Promise}
+   */
+  async hover(selector) {
+    let center = await this.evaluate(selector => {
+      let element = document.querySelector(selector);
+      if (!element)
+        return null;
+      element.scrollIntoViewIfNeeded();
+      let rect = element.getBoundingClientRect();
+      return {
+        x: (rect.left + rect.right) / 2,
+        y: (rect.top + rect.bottom) / 2
+      };
+    }, selector);
+    if (!center)
+      throw new Error('No node found for selector: ' + selector);
+    await this._frameManager._mouse.move(center.x, center.y);
+  }
+
+  /**
+   * @param {string} selector
+   * @param {!Object=} options
+   * @return {!Promise}
+   */
+  async click(selector, options) {
+    await this.hover(selector);
+    await this._frameManager._mouse.press(options);
+    // This is a hack for now, to make clicking less race-prone
+    await this.evaluate(() => new Promise(f => requestAnimationFrame(f)));
+  }
+
   /**
    * @param {?Object} framePayload
    */