Revert "Disable TabIconUpdated test on ChromeOS (is flaky)."

This reverts commit 7bf7db36.

Reason for revert: https://chromium-review.googlesource.com/c/1273515 has landed.

Original change's description:
> Disable TabIconUpdated test on ChromeOS (is flaky).
> 
> TBR=alph@chromium.org
> 
> Bug: 892310
> Change-Id: I6cefa7018520128cdf81d79a1ee467d5ef5859fe
> Reviewed-on: https://chromium-review.googlesource.com/c/1269339
> Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
> Commit-Queue: Joshua Pawlicki <waffles@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#597679}

TBR=alph@chromium.org,waffles@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 892310
Change-Id: Ibb6d9ffdfe2372e165eb0abb7db9a2f4a0d57a2f
Reviewed-on: https://chromium-review.googlesource.com/c/1275665Reviewed-by: François Beaufort <beaufort.francois@gmail.com>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
Cr-Commit-Position: refs/heads/master@{#598694}

chrome/browser/picture_in_picture/picture_in_picture_window_controller_browsertest.cc

@@ -329,14 +329,8 @@ IN_PROC_BROWSER_TEST_F(PictureInPicturePixelComparisonBrowserTest, VideoPlay) {
 
 // Tests that when an active WebContents accurately tracks whether a video
 // is in Picture-in-Picture.
-// Flaky failures on ChromeOS - http://crbug.com/892310
-#if defined(OS_CHROMEOS)
-#define MAYBE_TabIconUpdated DISABLED_TabIconUpdated
-#else
-#define MAYBE_TabIconUpdated TabIconUpdated
-#endif
 IN_PROC_BROWSER_TEST_F(PictureInPictureWindowControllerBrowserTest,
-                       MAYBE_TabIconUpdated) {
+                       TabIconUpdated) {
   GURL test_page_url = ui_test_utils::GetTestUrl(
       base::FilePath(base::FilePath::kCurrentDirectory),
       base::FilePath(