Cleanup: Rename http_message_test_utils.{h,cc,_test.cc} to

Cleanup: Rename http_message_test_utils.{h,cc,_test.cc} to
http_message.{h,cc,_test.cc}

This is how it should be named (defines/tests class HTTPMessage), and
it's confusingly similar to the unrelated http_message_utils.h

n/a (test only)

Merge internal change: 61955207

R=rch@chromium.org

[Ryan Hamilton, 2014-02-26 22:18:52]

lgtm