[Files app] Added method ConcurrentQueue.lock()

This convenience method allows usage patterns that are easier to read
and maintain, and promotes better error propagation by discouraging
exception swallowing.

Used it in VolumeManagerImpl.

Change-Id: Idfb1832d7262a37245fc818a063d3d36575d11b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1621480
Commit-Queue: François Degros <fdegros@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Auto-Submit: François Degros <fdegros@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662509}
3 files changed