In preparation for wider usage in media code, move the H.264 parser and
reader classes to media/filters from GPU-accelerated media locations, and
into the media namespace. These classes have only been, up to now, used
by hardware decode accelerators.

Also, move their unittests along and make them a part of media_unittests,
demoting H264ParserUnittest from being a standalone executable. While it
was designed to be run on a set of streams from commandline, it should make
more sense to run it more regularly (if only on just one stream), together
with media tests, to prevent basic regressions, if it's to be used more
widely than only in CrOS hardware acceleration classes.

BUG=None
TEST=Build VAVDA and vdaunittest for x86,
build EVDA, vdaunittest and veaunittest for ARM.
Also build and run media_unittests for both.

Review URL: https://codereview.chromium.org/119153002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244132 0039d316-1c4b-4281-b951-d872f2087c98