Added license header

chrome/common/extensions/docs/examples/api/tabs/screenshot/screenshot.js

+// Copyright (c) 2011 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.
+
 // To make sure we can uniquely identify each screenshot tab, add an id as a
 // query param to the url that displays the screenshot.
 var id = 100;
 
 function takeScreenshot() {
   chrome.tabs.captureVisibleTab(null, function(img) {
     var screenshotUrl = img;
     var viewTabUrl = [chrome.extension.getURL('screenshot.html'),
                       '?id=', id++].join('');
 
@@ skipping 26 matching lines @@
         }
       };
       chrome.tabs.onUpdated.addListener(addSnapshotImageToTab);
 
     });
   });
 }
 
 // Listen for a click on the camera icon.  On that click, take a screenshot.
 chrome.browserAction.onClicked.addListener(function(tab) {
-  takeScreenshot();
+  if (tab.url.match(/code.google.com/)) {
+    takeScreenshot();
+  } else {
+    alert('This sample can only take screenshots of code.google.com pages');
+  }
 });