fix(Navigation): correctly wait for navigation in Page.goto (#1355)

This patch:
- starts persisting lifecycle state for every frame
- migrates NavigationWatcher to rely on these lifecycle events
- refactors Page.goto to properly return navigation errors

Fixes #1218.

lib/FrameManager.js

@@ -41,10 +41,22 @@ class FrameManager extends EventEmitter {
     this._client.on('Page.frameNavigated', event => this._onFrameNavigated(event.frame));
     this._client.on('Page.frameDetached', event => this._onFrameDetached(event.frameId));
     this._client.on('Runtime.executionContextCreated', event => this._onExecutionContextCreated(event.context));
+    this._client.on('Page.lifecycleEvent', event => this._onLifecycleEvent(event));
 
     this._handleFrameTree(frameTree);
   }
 
+  /**
+   * @param {!Object} event
+   */
+  _onLifecycleEvent(event) {
+    const frame = this._frames.get(event.frameId);
+    if (!frame)
+      return;
+    frame._onLifecycleEvent(event.loaderId, event.name);
+    this.emit(FrameManager.Events.LifecycleEvent, frame);
+  }
+
   /**
    * @param {{frame: Object, childFrames: ?Array}} frameTree
    */
@@ -171,20 +183,14 @@ class FrameManager extends EventEmitter {
     this._frames.delete(frame._id);
     this.emit(FrameManager.Events.FrameDetached, frame);
   }
-
-  /**
-   * @return {?string}
-   */
-  unreachableMainFrameURL() {
-    return this._mainFrame._unreachableURL || null;
-  }
 }
 
 /** @enum {string} */
 FrameManager.Events = {
   FrameAttached: 'frameattached',
   FrameNavigated: 'framenavigated',
-  FrameDetached: 'framedetached'
+  FrameDetached: 'framedetached',
+  LifecycleEvent: 'lifecycleevent'
 };
 
 /**
@@ -205,6 +211,9 @@ class Frame {
     this._context = null;
     /** @type {!Set<!WaitTask>} */
     this._waitTasks = new Set();
+    this._loaderId = '';
+    /** @type {!Set<string>} */
+    this._lifecycleEvents = new Set();
 
     /** @type {!Set<!Frame>} */
     this._childFrames = new Set();
@@ -523,7 +532,18 @@ class Frame {
   _navigated(framePayload) {
     this._name = framePayload.name;
     this._url = framePayload.url;
-    this._unreachableURL = framePayload.unreachableUrl;
+  }
+
+  /**
+   * @param {string} loaderId
+   * @param {string} name
+   */
+  _onLifecycleEvent(loaderId, name) {
+    if (name === 'init') {
+      this._loaderId = loaderId;
+      this._lifecycleEvents.clear();
+    }
+    this._lifecycleEvents.add(name);
   }
 
   _detach() {