Make CompatFramework::ReportChange thread safe

Guard accesses to reported_compat_changes_ with
reported_compat_changes_lock_. Guarding disabled_compat_changes_ should
not be necessary, as it's initialized synchronously early after zygote
fork, never to be changed afterwards.

Bug: 174843201
Test: manual
Change-Id: I73b5dadf0576c2bc163602f566486172c35dd78d
2 files changed