Remove syncproto.h

Replace sync/engine/syncproto.h with sync/syncable/syncable_proto_util.h and
.cc.  The tasks that used to be performed by member functions of the syncer::
proto wrapper classes are now handled by static member functions.

Unfortunately, serialization and de-serialization of syncable::Id to/from proto
fields has gotten a bit uglier.  On the other hand, it's now much less magical
and mysterious.

The test intended to prevent regressions of crbug.com/134715 has been replaced
with a DCHECK.  We'll have to rely on it to ensure that the protocol_version
field is always explicitly set.

BUG=136454
TEST=


Review URL: https://chromiumcodereview.appspot.com/10735041

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@146393 0039d316-1c4b-4281-b951-d872f2087c98
35 files changed