OS: Win7

Based on 
https://chromium-review.googlesource.com/c/chromium/src/+/1128824/6
https://logs.chromium.org/logs/chromium/buildbucket/cr-buildbucket.appspot.com/8941308135576421056/+/steps/browser_tests__with_patch_/0/logs/HostedAppGlassBrowserFrameViewTest.ThemeColor/0
it seems that our Windows 7 try bots aren't running with Aero enabled meaning we're not getting Aero GlassBrowserFrameView coverage on Windows 7.

I think ideally the browser tests would be able to turn on/off Aero mode as required for testing.