[chromium-reviews] Add getLanguage function to tabs extension

chrome/test/data/extensions/good/Extensions/behllobkkfkfnphdnhnkndlbkcpglgmj/1.0.0.0/toolstrip1.html

 <script>
 // This function is called from the C++ browser test. It does a basic sanity
 // test that we can call extension APIs.
 function testTabsAPI() {
   console.log(chrome.tabs);
 
   chrome.tabs.getAllInWindow(null, function(tabs) {
     window.domAutomationController.send(tabs.length == 1);
   });
 }
+
+// This function is called from the C++ browser test. It tests the getLanguage
+// function to make sure it can be used as an extension API. This will pass if
+// the browser navigates to a page in French language before this is called.
+function testTabsLanguageAPI() {
+  chrome.tabs.getLanguage(null, function(language) {
+    window.domAutomationController.send(language == 'FRENCH');
+  });
+}
+
 </script>
 <select>
   <option>one</option>
   <option>two</option>
   <option>three</option>
 </select>