Extend simple loading test to relay a message for non-SFI NaCl.
Currently, the test only looks at whether the loading is successfully
done or not. This CL adds the test for PostMessage and HandleMessage.
The loading test is still covered by the new test.
BUG=https://code.google.com/p/nativeclient/issues/detail?id=3734
TEST=Ran browser_test --gtest_filter=NaCl*NonSfi*, and trybots.
Review URL: https://codereview.chromium.org/
208243015
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@259717 0039d316-1c4b-4281-b951-d872f2087c98