Prevent MediaBrowser.mRootHints from being modified in API 21+

When the browser and the service run in the same process in API 21+,
the MediaBrowserServiceCompat modifies MediaBrowser.mRootHints which
should not be changed. This CL fixes the problem by passing the copied
object of rootHints.

Bug: 36895063
Test: Run MediaBrowserCompatTest in API 19-25 and Android O
Change-Id: I1bf241740db69fc9aba3725a3bb16e0fbacfa169
2 files changed