Respect the clipboardRead and clipboardWrite permissions in content scripts.

chrome/test/data/extensions/api_test/clipboard/extension/content_script.js

+// Copyright 2014 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.
+
+// TODO(kalman): Consolidate this test script with the other clipboard tests.
+
+function appendTextarea() {
+  return document.body.appendChild(document.createElement('textarea'));
+}
+
+function run() {
+  var textIn = appendTextarea();
+
+  textIn.focus();
+  textIn.value = 'foobar';
+  textIn.selectionStart = 0;
+  textIn.selectionEnd = 'foobar'.length;
+  if (!document.execCommand('copy'))
+    return 'Failed to copy';
+
+  var textOut = appendTextarea();
+
+  textOut.focus();
+  if (!document.execCommand('paste'))
+    return 'Failed to paste';
+  if (textOut.value != 'foobar')
+    return 'Expected "foobar", got ' + textOut.value;
+
+  return '';
+}
+
+chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {
+  sendResponse(run());
+});