Add always-on-top property to app windows

chrome/test/data/extensions/platform_apps/windows_api_always_on_top/background.js

+// Copyright 2013 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.
+
+var callbackPass = chrome.test.callbackPass;
+
+function testAlwaysOnTop(testId, initValue) {
+  var options =
+    {
+      id: testId,
+      alwaysOnTop: initValue
+    };
+  chrome.app.window.create('index.html',
+                           options,
+                           callbackPass(function(win) {
+    chrome.test.assertEq(initValue, win.isAlwaysOnTop());
+    win.setAlwaysOnTop(!initValue);
+
+    setTimeout(callbackPass(function() {

[benwells, 2013/10/09 02:00:50]

Is there any way to test this without relying on a timeout of 500ms? This will
be flaky on the bots.

As we'd only be testing whether setting is set and retrieved properly, not that
the window is actually stay on top, maybe it isn't worth testing.

[tmdiep, 2013/10/09 06:18:08]

It is tricky to test whether the window is actually on top, so I didn't really
try.

This was an end-to-end test to verify that after calling SetAlwaysOnTop(),
IsAlwaysOnTop() will return the new value. I know this isn't a good solution,
but I increased the timeout to 2 secs. 

+      chrome.test.assertEq(!initValue, win.isAlwaysOnTop());
+      win.contentWindow.close();
+    }), 500);
+  }));
+}
+
+chrome.app.runtime.onLaunched.addListener(function() {
+  chrome.test.runTests([
+
+    // Window is created with always on top enabled, then disabled after
+    // creation.
+    function testAlwaysOnTopInitTrue() {
+      testAlwaysOnTop('testAlwaysOnTopInitTrue', true);
+    },
+
+    // Window is created with always on top disabled, then enabled after
+    // creation.
+    function testAlwaysOnTopInitFalse() {
+      testAlwaysOnTop('testAlwaysOnTopInitFalse', false);
+    }
+
+  ]);
+});