Min/max/close stay on what system theme was at launch

[mathewleeza]

Dev Home version

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Windows build number

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Other software

Steps to reproduce the bug

Min/max/close have incorrect theming when in dark theme

Expected result

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Actual result

Min/max/close have incorrect theming when in dark theme

Included System Information

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Included Extensions Information

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[krschau]

Behavior I'm seeing on 0.14 canary:

1. System theme dark, DH theme dark, icons are good. Change DH theme to light, icons don't update
2. System theme dark, DH theme light, icons are using dark theme. Change DH theme to dark and the icons now look right.