Update references to the extension messaging APIs to point to the "runtime"

chrome/test/data/extensions/api_test/tabs/capture_visible_tab/test_race.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.
 //
 // API test for chrome.tabs.captureVisibleTab() that tests that concurrent
 // capture requests end up with the expected data (by opening 8 windows with
 // alternating black and white contents and asserting that the captured pixels
 // are of the expected colors).
 // browser_tests.exe --gtest_filter=ExtensionApiTest.CaptureVisibleTabRace
 
@@ skipping 46 matching lines @@
 
       var testedWindowCount = 0;
       windowsAndColors.forEach(function(windowIdAndExpectedColor) {
         var windowId = windowIdAndExpectedColor[0];
         var expectedColor = windowIdAndExpectedColor[1];
         chrome.tabs.captureVisibleTab(
             windowId,
             {'format': 'png'},
             function(imgDataUrl) {
               log('captured ' + windowId);
-              if (chrome.extension.lastError) {
+              if (chrome.runtime.lastError) {
                 chrome.test.fail('captureVisibleTab error: ' +
-                    chrome.extension.lastError.message);
+                    chrome.runtime.lastError.message);
               }
               testPixelsAreExpectedColor(
                   imgDataUrl, kWindowRect, expectedColor);
               log('tested pixels for ' + windowId);
               testedWindowCount++;
               if (testedWindowCount == windowsAndColors.length) {
                 log('test complete');
                 callbackCompleted();
               }
             });
       });
     });
  }
 ]);