We shouldn't have protocol constraints that are sensitive to whether
data is returned synchronously or not.
Per https://boringssl-review.googlesource.com/#/c/4112/, the original
limitation was to avoid OpenSSL ABI changes. This is no longer a
concern.
Add tests for the sync and async case. Send the empty records in two
batches to ensure the count is reset correctly.
Change-Id: I3fee839438527e71adb83d437879bb0d49ca5c07
Reviewed-on: https://boringssl-review.googlesource.com/5040
Reviewed-by: Adam Langley <agl@google.com>
a8ebe2261f