[Mac] Disable AppControllerPlatformAppBrowserTest.ActivationFocusesBrowserWindow due to flakes.

Bug: 1158888
Change-Id: I0815f5e83219324b167eb7a7e608382754d9e15c
Tbr: avi@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2593690Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837187}

chrome/browser/app_controller_mac_browsertest.mm

@@ -219,7 +219,7 @@ IN_PROC_BROWSER_TEST_F(AppControllerPlatformAppBrowserTest,
 }
 
 IN_PROC_BROWSER_TEST_F(AppControllerPlatformAppBrowserTest,
-                       ActivationFocusesBrowserWindow) {
+                       DISABLED_ActivationFocusesBrowserWindow) {
   AppController* app_controller = base::mac::ObjCCast<AppController>(
       [[NSApplication sharedApplication] delegate]);
   ASSERT_TRUE(app_controller);