[shell] Set DesktopView to black when no contents are loaded
This is better than the ContainmentView default of clear as it means we don't get garbage from the root window. CCBUG: 423545 CCBUG: 421237
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This is better than the ContainmentView default of clear as it means we don't get garbage from the root window. CCBUG: 423545 CCBUG: 421237
mentioned in commit b16ab4a1