Fix CRD opens a window every time it's clicked in the launcher

Cause:
This is a regression of the HRD change, in which we pass in an unique
ID everytime when we create an app window.  This causes a new window
to be created whenever the user clicks on the app icon in the app
launcher.

Fix:
Only create a new app window when:
1. There are no existing windows or
2. The user clicks on the New Window context menu

BUG=448128

Review URL: https://codereview.chromium.org/844503007

Cr-Commit-Position: refs/heads/master@{#311545}

remoting/webapp/crd/js/background.js

@@ -7,33 +7,58 @@ var remoting = remoting || {};
 
 (function(){
 
-/** @param {remoting.AppLauncher} appLauncher */
-function initializeAppV2(appLauncher) {
-  /** @type {string} */
-  var kNewWindowId = 'new-window';
-
-  /** @param {OnClickData} info */
-  function onContextMenu(info) {
-    if (info.menuItemId == kNewWindowId) {
-      appLauncher.launch();
-    }
-  }
+/**
+ * A class that handles application activation.
+ *
+ * @param {remoting.AppLauncher} appLauncher
+ * @constructor
+ */
+function ActivationHandler(appLauncher) {
+  /**
+   * @type {remoting.AppLauncher}
+   * @private
+   */
+  this.appLauncher_ = appLauncher;
 
-  function initializeContextMenu() {
   chrome.contextMenus.create({
-       id: kNewWindowId,
+     id: ActivationHandler.NEW_WINDOW_MENU_ID_,
      contexts: ['launcher'],
      title: chrome.i18n.getMessage(/*i18n-content*/'NEW_WINDOW')
   });
-    chrome.contextMenus.onClicked.addListener(onContextMenu);
-  }
 
-  initializeContextMenu();
-  chrome.app.runtime.onLaunched.addListener(
-      appLauncher.launch.bind(appLauncher)
-  );
+  chrome.contextMenus.onClicked.addListener(this.onContextMenu_.bind(this));
+  chrome.app.runtime.onLaunched.addListener(this.onLaunched_.bind(this));
 }
 
+/** @type {string} */
+ActivationHandler.NEW_WINDOW_MENU_ID_ = 'new-window';
+
+/**
+ * @param {OnClickData} info
+ * @private
+ */
+ActivationHandler.prototype.onContextMenu_ = function(info) {
+  if (info.menuItemId == ActivationHandler.NEW_WINDOW_MENU_ID_) {
+    this.appLauncher_.launch();
+  }
+};
+
+/**
+ * Called when the App is activated (e.g. from the Chrome App Launcher).  It
+ * creates a new window if there are no existing ones.  Otherwise, it will put
+ * focus on the last window created.
+ *
+ * @private
+ */
+ActivationHandler.prototype.onLaunched_ = function() {
+  var windows = chrome.app.window.getAll();
+  if (windows.length >= 1) {
+    windows[windows.length - 1].focus();
+  } else {
+    this.appLauncher_.launch();
+  }
+};
+
 /**
  * The background service is responsible for listening to incoming connection
  * requests from Hangouts and the webapp.
@@ -61,8 +86,7 @@ function initializeBackgroundService(appLauncher) {
 
 function main() {
   if (base.isAppsV2()) {
-    var appLauncher = new remoting.V2AppLauncher();
-    initializeAppV2(appLauncher);
+    new ActivationHandler(new remoting.V2AppLauncher());
   }
 }
 

remoting/webapp/js_proto/chrome_proto.js

@@ -41,7 +41,11 @@ chrome.app.window = {
    * @param {string} id
    * @param {function()=} opt_callback
    */
-  get: function(id, opt_callback) {}
+  get: function(id, opt_callback) {},
+  /**
+   * @return {Array.<AppWindow>}
+   */
+  getAll: function() {}
 };