re-land r159362 ("Wait for content_shell to print #READY") w/ fix for android.

This re-lands the change in 159362 without the bug that was causing
run-webkit-tests to deadlock on startup on Android - we were attempting to
wait for the #READY before all of the android-specific scaffolding like the
forwarder had been started, and would never see any output.

R=ojan@chromium.org
BUG=265088

Review URL: https://codereview.chromium.org/26342008

git-svn-id: svn://svn.chromium.org/blink/trunk@159603 bbb929c8-8fbe-4397-9dbb-9b2b20218538