Update tabCapture API docs with browser action info.

chrome/test/data/extensions/api_test/tab_capture/experimental/active_tab_permission_test.js

Index: chrome/test/data/extensions/api_test/tab_capture/experimental/active_tab_permission_test.js
diff --git a/chrome/test/data/extensions/api_test/tab_capture/experimental/active_tab_permission_test.js b/chrome/test/data/extensions/api_test/tab_capture/experimental/active_tab_permission_test.js
index 6d0a4be8b7906437da9eeddd325faf485b32c7eb..405f361831e422a813be2220fa4f066a4c86e03a 100644
--- a/chrome/test/data/extensions/api_test/tab_capture/experimental/active_tab_permission_test.js
+++ b/chrome/test/data/extensions/api_test/tab_capture/experimental/active_tab_permission_test.js
@@ -28,7 +28,8 @@ var afterGrantPermission = function(msg) {
 var afterOpenTab = function(msg) {
   chrome.tabCapture.capture({audio: true, video: true}, function(stream) {
     chrome.test.assertLastError(
-      'Capture of this tab must be granted by clicking on the extension icon.');
+      'Capture of this tab must be granted through a user action (see the ' +
+      'activeTab permission). Chrome pages cannot be captured.');
     chrome.test.assertTrue(!stream);
 
     chrome.test.sendMessage('ready2', afterGrantPermission);