Disable two flaky tests on ChromeOS

Disable ShelfLayoutManagerTest.FlingUpOnShelfForFullscreenAppList
Disable WindowSelectorTest.RoundedEdgeMaskVisibility

Tbr: xiyuan, xdai
Bug: 864467, 864465
Change-Id: I77a0dbcddad5176575f0dc5991beb9eef8090167
Reviewed-on: https://chromium-review.googlesource.com/1140683
Reviewed-by: Owen Min <zmin@chromium.org>
Commit-Queue: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575707}
2 files changed