Use stream operators for appending to InfoLog. Also add a helper class to keep the previous behaviour of automatically appending a newline after every new message. BUG=angleproject:992 Change-Id: I0ff5d2846175cf19de7a6af295af24a92451456f Reviewed-on: https://chromium-review.googlesource.com/268744 Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>