18d74fe45 Show test output when engine unit test fails. (flutter/engine#14026) (#45675)

git@github.com:flutter/engine.git/compare/e3e5f8dabc2e...18d74fe45b9c

git log e3e5f8dabc2e..18d74fe45b9c --first-parent --oneline
2019-11-27 flar@google.com Show test output when engine unit test fails. (#14026)


If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
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Please CC cbracken@google.com on the revert to ensure that a human
is aware of the problem.

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