Hook up TaskDescription into set bar color calls (6/N)

This patch will update the task description when the app calls
setStatusBarColor or setNavigationBarColor. The status bar is updated
but the information is not reflected in the task description without
this patch.

Bug: 132756841
Bug: 113253712
Test: Test with the test app in b/132756841. The task description is
      updated as expected.
Test: go/wm-smoke
Change-Id: I4ba1e5e7dd0f096cba40221450a8861e3d578e3c