Revert "Release bitmap reference right after Per85ComputeTask done its job."

This reverts commit 1e0e143c.

Reason for revert:
ART remove preloaded classes in ag/6987683 to prevent AsyncTask leakage.
1. android.content.AsyncTaskLoader$LoadTask
2. android.speech.tts.TextToSpeech$Connection$SetupConnectionAsyncTask

Bug: 124127996
Bug: 130206915
Test: Obtain CL ag/6987683 in local test environment.
Test: run "atest android.app.cts.WallpaperManagerTest".
Test: Observe AsyncTask do not cause bitmap object leak anymore.
Change-Id: I358756366fd9a08bbdd51e09f21fccafee7ad311