Revert "Disable CustomFrameViewAshTest.ActiveStateOfButtonMatchesWidget on linux-chromeos-rel"

This reverts commit 323e8611.

Reason for revert: Disabled non-offending test

Original change's description:
> Disable CustomFrameViewAshTest.ActiveStateOfButtonMatchesWidget on linux-chromeos-rel
> 
> It is flaking.
> 
> TBR=sky@chromium.org
> 
> Bug: 869830
> Change-Id: Id455349e683f1adda690457faffc40d12c977d38
> Reviewed-on: https://chromium-review.googlesource.com/1158584
> Reviewed-by: Christos Froussios <cfroussios@chromium.org>
> Commit-Queue: Christos Froussios <cfroussios@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#579789}

TBR=cfroussios@chromium.org

Change-Id: I1904d3f8febf2d9c0fcac0032e2622df2bdb009d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 869830
Reviewed-on: https://chromium-review.googlesource.com/1160222Reviewed-by: Christos Froussios <cfroussios@chromium.org>
Commit-Queue: Christos Froussios <cfroussios@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580115}

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

@@ -479,14 +479,8 @@ IN_PROC_BROWSER_TEST_P(BrowserNonClientFrameViewAshTest,
 }
 
 // Regression test for https://crbug.com/839955
-// TODO(crbug.com/869830) The test is flaky on ChromeOS rel.
-#if defined(OS_CHROMEOS) && defined(NDEBUG)
-#define MAYBE_ActiveStateOfButtonMatchesWidget DISABLED_ActiveStateOfButtonMatchesWidget
-#else
-#define MAYBE_ActiveStateOfButtonMatchesWidget ActiveStateOfButtonMatchesWidget
-#endif
 IN_PROC_BROWSER_TEST_P(BrowserNonClientFrameViewAshTest,
-                       MAYBE_ActiveStateOfButtonMatchesWidget) {
+                       ActiveStateOfButtonMatchesWidget) {
   BrowserView* browser_view = BrowserView::GetBrowserViewForBrowser(browser());
 
   ash::FrameCaptionButtonContainerView::TestApi test(