Disable TrayAccessibilityTest.ShowMenuWithShowMenuOption on Linux.

As tests are failing on linux-chromeos-dbg (which apparently does not set OS_CHROMEOS
so disable the test on linux instead).

TBR=yoshiki@chromium.org

Change-Id: I4bf298ed79ff4fb20174d493594e61e55c94dfa4
BUG: 1027919

Change-Id: I39ab2707f53185be90781796747e7b20b039202e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1932658Reviewed-by: Tim Schumann <tschumann@chromium.org>
Commit-Queue: Tim Schumann <tschumann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718478}

chrome/browser/chromeos/system/tray_accessibility_browsertest.cc

@@ -321,7 +321,7 @@ IN_PROC_BROWSER_TEST_P(TrayAccessibilityTest, ShowMenu) {
 }
 
 // Fails on linux-chromeos-dbg see crbug/1027919.
-#if defined(OS_CHROMEOS)
+#if defined(OS_LINUX)
 #define MAYBE_ShowMenuWithShowMenuOption DISABLED_ShowMenuWithShowMenuOption
 #else
 #define MAYBE_ShowMenuWithShowMenuOption ShowMenuWithShowMenuOption