Rename SharedContexMutex into ContexMutex Follow up after: Replace (Single/Shared)ContextMutex classed with ContextMutex Renamed build option: angle_enable_shared_context_mutex -> angle_enable_context_mutex Renamed because there is no more SharedContexMutex class and ContextMutex is now used for both Shared and not Shared Contexts. Bug: angleproject:8226 Change-Id: I68eea84aa59441d9c5b19870910b2bb499311e08 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4650350 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Igor Nazarov <i.nazarov@samsung.com>