Handle app custom icon via aura::Window property.

chrome/test/data/extensions/platform_apps/app_icon/test.js

 // Copyright (c) 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.
 
-chrome.app.runtime.onLaunched.addListener(function() {
-  chrome.test.sendMessage("Launched");
-  // Create a panel window first
-  chrome.app.window.create(
-    'main.html', { type: "panel" },
-    function (win) {
-      // Set the panel window icon
-      win.setIcon("icon64.png")
+var panelWindow;
+var nonShelfWindow;
+var shelfWindow;
+
+function processNextCommand() {
+  chrome.test.sendMessage('ready', function(response) {
+    if (response == 'Exit') {
+      return;
+    }
+    if (response == 'createPanelWindow') {
+      chrome.app.window.create('main.html', { type: 'panel' }, function (win) {
+         panelWindow = win;
+      });
+    }
+    if (response == 'setPanelWindowIcon') {
+      panelWindow.setIcon('icon64.png')
+    }
+    if (response == 'createNonShelfWindow') {
       // Create the shell window; it should use the app icon, and not affect
       // the panel icon.
       chrome.app.window.create(
-        'main.html', { type: "shell" },
+        'main.html', { id: 'win',
+                       type: 'shell' },
         function (win) {
-          // Create the shell window which is shown in shelf; it should use
-          // another custom app icon.
-          chrome.app.window.create(
-            'main.html', { id: "win_with_icon",
-                           type: "shell",
-                           icon: "icon48.png",
-                           showInShelf: true },
-            function (win) {
-              chrome.test.sendMessage("Completed");
-            });
+            nonShelfWindow = win;
         });
-    });
+    }
+    if (response == 'createShelfWindow') {
+      // Create the shell window which is shown in shelf; it should use
+      // another custom app icon.
+      chrome.app.window.create(
+        'main.html', { id: 'win_with_icon',
+                       type: 'shell',
+                       showInShelf: true },
+        function (win) {
+          shelfWindow = win;
+        });
+    }
+    if (response == 'setShelfWindowIcon') {
+      shelfWindow.setIcon('icon32.png')
+    }
+    processNextCommand();
+  });
+};
+
+
+chrome.app.runtime.onLaunched.addListener(function() {
+  chrome.test.sendMessage('Launched');
+  processNextCommand();
 });
+