Leave fullscreen mode in an app window when ESC key is pressed.

chrome/test/data/extensions/platform_apps/prevent_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 will prevent the default behavior for
+    // the ESC key, thus will prevent the ESC key to leave fullscreen.
+    win.contentWindow.document.addEventListener('keydown', function(e) {
+      e.preventDefault();
+    });
+    win.contentWindow.document.addEventListener('keyup', function(e) {
+      e.preventDefault();
+    });
+
+    chrome.test.sendMessage('Launched', function(reply) {
+      var doc = win.contentWindow.document;
+
+      switch (reply) {
+        case 'window':
+          doc.addEventListener('keydown', function(e) {
+            if (e.keyCode != 66) // 'b'
+              return;
+            doc.removeEventListener('keydown', arguments.callee);
+            // We do one trip to the event loop to increase the chances that
+            // fullscreen could have been left before the message is received.
+            setTimeout(function() {
+              chrome.test.sendMessage('B_KEY_RECEIVED');
+            });
+          });
+          win.fullscreen();
+          break;
+
+        case 'dom':
+          doc.addEventListener('keydown', function() {
+            doc.removeEventListener('keydown', arguments.callee);
+
+            doc.addEventListener('keydown', function(e) {
+              if (e.keyCode != 66) // 'b'
+                return;
+              doc.removeEventListener('keydown', arguments.callee);
+              // We do one trip to the event loop to increase the chances that
+              // fullscreen could have been left before the message is received.
+              setTimeout(function() {
+                chrome.test.sendMessage('B_KEY_RECEIVED');
+              });
+            });
+
+            doc.body.webkitRequestFullscreen();
+          });
+          break;
+      }
+    });
+  });
+});