This "child" test was actually reading itself (whoops!). Instead, pass
the address of the string to be read back from the child and read that.
Bug: crashpad:196
Change-Id: I27aa4cd06c69cd492cb3387a5a773a56e9cb02a3
Reviewed-on: https://chromium-review.googlesource.com/1033712
Reviewed-by: Joshua Peraza <jperaza@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>