Fix ExtensionWindowCreateTest.AcceptState flakiness on Mac
Fix ExtensionWindowCreateTest.AcceptState flakiness on Mac

This switches ExtensionWindowCreateTest.AcceptState to use
ScopedFakeNSWindowFullscreen which is mocks out -[NSWindow toggleFullscreen:]

BUG=482433

Review URL: https://codereview.chromium.org/1427743007

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#358220}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk