Rework the way we initialize devices on Android in run-webkit-tests.

This restructures the Android port code so that we push the executables
and other files in parallel as part of port.check_build() and port.setup_test_run(),
so that we don't need to push code in the child processes when we're actually trying to run tests.

R=ojan@chromium.org, peter@chromium.org, abarth@chromium.org
BUG=276077

Review URL: https://chromiumcodereview.appspot.com/23868015

git-svn-id: svn://svn.chromium.org/blink/trunk@157728 bbb929c8-8fbe-4397-9dbb-9b2b20218538