Functionality has been requested in the Extension API for Javascript to...

chrome/renderer/extensions/extension_api_client_unittest.cc

 // Copyright (c) 2009 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.
 
 #include "base/file_util.h"
 #include "base/path_service.h"
 #include "base/string_util.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/render_messages.h"
 #include "chrome/renderer/extensions/extension_process_bindings.h"
@@ skipping 404 matching lines @@
                "Uncaught Error: Invalid value for argument 1. "
                "Expected 'function' but got 'integer'.");
 
   ExpectJsPass("chrome.tabs.remove(2, function(){})",
                "tabs.remove", "2");
 
   ExpectJsPass("chrome.tabs.remove(2)",
                "tabs.remove", "2");
 }
 
+TEST_F(ExtensionAPIClientTest, CaptureVisibleTab) {
+  ExpectJsFail("chrome.tabs.captureVisibleTab(0);",
+               "Uncaught Error: Parameter 1 is required.");
+
+  ExpectJsFail("chrome.tabs.captureVisibleTab(function(){}, 0)",
+               "Uncaught Error: Invalid value for argument 0. "
+               "Expected 'integer' but got 'function'.");
+
+  ExpectJsPass("chrome.tabs.captureVisibleTab(null, function(img){});",
+               "tabs.captureVisibleTab", "null");
+}
+
 // Bookmark API tests
 // TODO(erikkay) add more variations here
 
 TEST_F(ExtensionAPIClientTest, CreateBookmark) {
   ExpectJsFail(
       "chrome.bookmarks.create({parentId:0, title:0}, function(){})",
       "Uncaught Error: Invalid value for argument 0. "
       "Property 'parentId': Expected 'string' but got 'integer', "
       "Property 'title': Expected 'string' but got 'integer'.");
 
@@ skipping 117 matching lines @@
                "toolstrip.collapse",
                "\"http://foo/\"");
 
   ExpectJsFail("chrome.toolstrip.collapse(100)",
                "Uncaught Error: Invalid value for argument 0. "
                "Expected 'string' but got 'integer'.");
   ExpectJsFail("chrome.toolstrip.collapse('http://foo/', 32)",
                "Uncaught Error: Invalid value for argument 1. "
                "Expected 'function' but got 'integer'.");
 }