Flip --enable-apps-show-on-first-paint flag.

chrome/test/data/extensions/platform_apps/leave_fullscreen/main.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.
 
 chrome.app.runtime.onLaunched.addListener(function() {
   chrome.app.window.create('main.html', {}, function(win) {
-    // The following key events handler should have no effect because the
-    // application does not have the 'overrideEscFullscreen' permission.
-    win.contentWindow.document.addEventListener('keydown', function(e) {
-      e.preventDefault();
-    });
-    win.contentWindow.document.addEventListener('keyup', function(e) {
-      e.preventDefault();
-    });
-
-    chrome.test.sendMessage('Launched', function(reply) {
+    win.onWindowFirstShown.addListener(function() {
+      // The following key events handler should have no effect because the
+      // application does not have the 'overrideEscFullscreen' permission.
       win.contentWindow.document.addEventListener('keydown', function(e) {
-        if (e.keyCode != 90) // 'z'
-          return;
-
-        chrome.test.sendMessage('KeyReceived');
+        e.preventDefault();
+      });
+      win.contentWindow.document.addEventListener('keyup', function(e) {
+        e.preventDefault();
       });
 
-      switch (reply) {
-        case 'window':
-          win.fullscreen();
-          break;
-        case 'dom':
-          win.contentWindow.document.addEventListener('keydown', function() {
-            win.contentWindow.document.removeEventListener('keydown',
-                                                           arguments.callee);
-            win.contentWindow.document.body.webkitRequestFullscreen();
-          });
-          break;
-      }
+      chrome.test.sendMessage('Launched', function(reply) {
+        win.contentWindow.document.addEventListener('keydown', function(e) {
+          if (e.keyCode != 90) // 'z'
+            return;
+
+          chrome.test.sendMessage('KeyReceived');
+        });
+
+        switch (reply) {
+          case 'window':
+            win.fullscreen();
+            break;
+          case 'dom':
+            win.contentWindow.document.addEventListener('keydown', function() {
+              win.contentWindow.document.removeEventListener('keydown',
+                                                             arguments.callee);
+              win.contentWindow.document.body.webkitRequestFullscreen();
+            });
+            break;
+        }
+      });
     });
   });
 });