Reverting 22324. Reenables CustomHomePagesModelTest.ModelChangedNotification on Mac.

BUG=http://crbug.com/17452
TEST=Test should not be flaky.
Review URL: http://codereview.chromium.org/193058

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@25731 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/cocoa/custom_home_pages_model_unittest.mm

@@ -132,8 +132,7 @@ TEST_F(CustomHomePagesModelTest, KVO) {
 @end
 
 // Test that when individual items are changed that they broadcast a message.
-// Crashy, see http://crbug.com/17452.
-TEST_F(CustomHomePagesModelTest, DISABLED_ModelChangedNotification) {
+TEST_F(CustomHomePagesModelTest, ModelChangedNotification) {
   scoped_nsobject<CustomHomePageHelper> kvo_helper(
       [[CustomHomePageHelper alloc] init]);
   [[NSNotificationCenter defaultCenter]