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- Adds tests for existing implementation.
- Minor code change to reject certain invalid messages.

NOTE: The existing code just ignored the target name field if it
had length and/or offset outside the bounds of the message. This
change explicitly rejects that case in order to test that the
behavior is correct.

BUG=chromium:22532
TEST=builds and tests pass

Review-Url: https://codereview.chromium.org/2873673002
Cr-Commit-Position: refs/heads/master@{#486604}