So that other components can get app icon throught it as well.
Like showing app icon as resizing hint while dragging divider bar in
split screen.
Bug: 201653912
Test: atest WMShellUnitTests
Merged-In: If4ab0590f4b850103411b6a2dccf2092bb06d563
Change-Id: Ia99fd2b9ddb05b95205bf923a1ac0f3922e54db7