Merge remote-tracking branch 'origin/master' into ghm 

Merge remote-tracking branch 'origin/master' into ghm 

Merge remote-tracking branch 'origin/master' into ghm 

Merge remote-tracking branch 'origin/master' into ghm 

Merge remote branch 'origin/master' into GitHub 

[M56] readme update for cpp/unity, also version and guid updates PiperOrigin-RevId: 270787142

Remove test files that have secrets, and allow non-secrets to be pass… …ed through Copybara PiperOrigin-RevId: 268032050

Fixed some potential race conditions in DatabaseReference's various constructors. Because the database keeps its own bookkeeping regarding the memory addresses of the QueryInternals and DatabaseReferenceInternals, if they are created and added to the Database's registry in two steps, a situation could arise where the database shuts down with either stale or incomplete internal bookkeeping. To solve this, any place that we update Database's bookkeeping we need do so atomically. PiperOrigin-RevId: 265136296

Moved output value for EXPECT_DEATH to define so can be set to differ… …ent values on different platforms. Fixes a bunch of unit tests. PiperOrigin-RevId: 263259596

Update dynamic links Android build's compile SDK version Missed updating a number to 28. While not technically necessary, since the targetSdkVersion is 28, for consistency with the other libraries dynamic links should be updated as well. PiperOrigin-RevId: 256039327