Reenable HitTestTabstrip for ChromeOS

BrowserNonClientFrameViewTabbedTest.HitTestsTabStrip was disabled
due to flakiness caused by a class that was not properly cleaned up
between tests.  This issue has now been resolved and this test is
being re-enabled.

Still flaky for TSAN.  Updated TODO to reflect the TSAN bug.

Bug: 1015949
Change-Id: I3ecbc316369742ab40cf5abba7ea8f247dff8d48
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1951650
Commit-Queue: Sean Kau <skau@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721724}

chrome/browser/ui/views/frame/browser_non_client_frame_view_unittest.cc

@@ -74,8 +74,8 @@ class BrowserNonClientFrameViewTabbedTest
       : BrowserNonClientFrameViewTest(Browser::TYPE_NORMAL) {}
 };
 
-// TODO(crbug.com/1015949): Flaky on ChromeOS and Linux TSAN.
-#if defined(OS_CHROMEOS) || (defined(OS_LINUX) && defined(THREAD_SANITIZER))
+// TODO(crbug.com/1011339): Flaky on Linux TSAN.
+#if defined(OS_LINUX) && defined(THREAD_SANITIZER)
 #define MAYBE_HitTestTabstrip DISABLED_HitTestTabstrip
 #else
 #define MAYBE_HitTestTabstrip HitTestTabstrip