[Sheriff] Disable TabletModeControllerScreenshotTest.ScreenshotVisibility.

Disalbe test TabletModeControllerScreenshotTest.ScreenshotVisibility
because it is crash on some builders. See the bug for more details.

BUG=1091085
TBR=skuhne@chromium.org

Change-Id: I8383c7dc9cb17f4271d18d35b5fc3a315fa67b76
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2228438Reviewed-by: Maggie Cai <mxcai@chromium.org>
Commit-Queue: Maggie Cai <mxcai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774978}

ash/wm/tablet_mode/tablet_mode_controller_unittest.cc

@@ -1776,7 +1776,8 @@ TEST_P(TabletModeControllerScreenshotTest, EnterTabletModeWhileAnimating) {
 
 // Tests that the screenshot is visible when a window animation happens when
 // entering tablet mode.
-TEST_P(TabletModeControllerScreenshotTest, ScreenshotVisibility) {
+// Crashes on Linux Chrome OS.  http://crbug.com/1091085
+TEST_P(TabletModeControllerScreenshotTest, DISABLED_ScreenshotVisibility) {
   auto window = CreateTestWindow(gfx::Rect(200, 200));
   auto window2 = CreateTestWindow(gfx::Rect(300, 200));