Enable all ESC-Fullscreen tests (Chrome Apps) for all platforms.

chrome/test/data/extensions/platform_apps/leave_fullscreen/main.js

Index: chrome/test/data/extensions/platform_apps/leave_fullscreen/main.js
diff --git a/chrome/test/data/extensions/platform_apps/leave_fullscreen/main.js b/chrome/test/data/extensions/platform_apps/leave_fullscreen/main.js
index 109bccf88f97724024efc2dab190a1b785632da4..95940b1c3f67c163a0088d040af1dc6863aaaf7d 100644
--- a/chrome/test/data/extensions/platform_apps/leave_fullscreen/main.js
+++ b/chrome/test/data/extensions/platform_apps/leave_fullscreen/main.js
@@ -14,6 +14,13 @@ chrome.app.runtime.onLaunched.addListener(function() {
     });
 
     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();