Split lock in FontManagerService.

Split the lock for mUpdatableFontDir from mSerializedFontMap, so that
mSerializedFontMap can be used even during performing font updates.

Bug: 179103383
Test: atest FrameworksServicesTests:UpdatableFontDirTest
Change-Id: Ic3d3ee6f3cccfcbe86996b67543fc5fdc64c85aa
2 files changed