Prerender: re-enable NoStatePrefetchBrowserTest.AppCacheRegistered.

crrev.com/c/668373 seems to have eliminated the flakiness of
NoStatePrefetchBrowserTest.AppCacheRegistered on linux and windows
platforms. This CL renables the test on Mac as well.

Bug: 733504
Change-Id: I0bae4b3eea4220dc70e8189b4c3b20bde1d4e754
Reviewed-on: https://chromium-review.googlesource.com/684334Reviewed-by: Alexandr Ilin <alexilin@chromium.org>
Commit-Queue: Matthew Cary <mattcary@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504324}

chrome/browser/prerender/prerender_nostate_prefetch_browsertest.cc

@@ -731,13 +731,7 @@ IN_PROC_BROWSER_TEST_P(NoStatePrefetchBrowserTest, AppCacheHtmlInitialized) {
 
 // If a page has been cached by another AppCache, the prefetch should be
 // canceled.
-// Flaky on mac crbug.com/733504
-#if defined(OS_MACOSX)
-#define MAYBE_AppCacheRegistered DISABLED_AppCacheRegistered
-#else
-#define MAYBE_AppCacheRegistered AppCacheRegistered
-#endif
-IN_PROC_BROWSER_TEST_P(NoStatePrefetchBrowserTest, MAYBE_AppCacheRegistered) {
+IN_PROC_BROWSER_TEST_P(NoStatePrefetchBrowserTest, AppCacheRegistered) {
   base::TimeTicks current_time = GetPrerenderManager()->GetCurrentTimeTicks();
   auto* clock = OverridePrerenderManagerTimeTicks();
   // Some navigations have already occurred in test setup. In order to track