Cherry pick Make WebViewUpdateService a SystemService. DO NOT MERGE

Migrate WebViewUpdateService to the newer SystemService approach instead
of ServiceManager.addService.

Original Bug: 16403706
Original Change-Id: I21aa67a41c22c3c20ba9e82eb87e5d610fe130e8

Bug: 16723226
Change-Id: Id276b71ee547e683f0756bcee0f4978ce342c2af
2 files changed