Make the SSLServerSocket unittests less crashy
Make the SSLServerSocket unittests less crashy

Currently, the SSLServerSocket tests can be non-deterministically crashy
when preconditions fail, due to use of CHECKS and not ASSERT_ing that
returned/created pointers are valid before using. To make the tests
more robustly deterministic in the face of failure, and to avoid making
memory bots extra sad, liberally sprinkle ASSERT_*s throughout the
code to ensure that all pre-conditions of the code under test are
valid.

BUG=none
R=eroman@chromium.org

Review URL: https://codereview.chromium.org/1782273002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#380548}

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