[iOS] Disable BrowserListImplTest.BrowserListObserver

This test is failing ~95% of the time on simulator as well, so
disabling it pending further investigation.

Bug: 1043625
Change-Id: I60d1193297633545153ff537747739c1e5aec370
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2057524Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741567}

ios/chrome/browser/main/browser_list_impl_unittest.mm

@@ -136,13 +136,8 @@ TEST_F(BrowserListImplTest, AllBrowserValuesDontChange) {
 
 // Check that an observer is informed of additions and removals to both the
 // regular and incognito browser lists.
-// TODO(crbug.com/1043625): Fails on device.
-#if TARGET_IPHONE_SIMULATOR
-#define MAYBE_BrowserListObserver BrowserListObserver
-#else
-#define MAYBE_BrowserListObserver DISABLED_BrowserListObserver
-#endif
-TEST_F(BrowserListImplTest, MAYBE_BrowserListObserver) {
+// TODO(crbug.com/1043625): Fails on device and simulator
+TEST_F(BrowserListImplTest, DISABLED_BrowserListObserver) {
   TestBrowserListObserver* observer = new TestBrowserListObserver;
   browser_list_->AddObserver(observer);