Partially revert ag/10355722 to fix perf regression

Creating WindowContexts too often caused a regression. Reverting the
MediaArtworkProcessor changes and marking to suppress warning for now.

Bug created to find a solution.

Fixes: 150813031
Bug: 150805950
Test: MediaArtworkProcessorTest
Change-Id: Ia928bd8d8b0d21f4370ad5a34d008782c77272df