Fix DrMemory bots for real.

The bot config passes an empty "" parameter, which makes optparse stop parsing
arguments -- on linux, the empty parameter gets filtered out before reaching
this script. There's no reason to stop option parsing on the first non-flag
as far as I can see, so don't do that.

See the bug for details.

BUG=305292
NOTRY=true

Review URL: https://codereview.chromium.org/26548002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227601 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227601
Docserver: Pull knowledge of host file systems into a single
HostFileSystemProvider class, basically a rename of HostFileSystemCreator with
a stricter notion of trunk vs branches.

In some ways this is a follow-up to r218556, except solving the problem in a
type-safe (rather than special-case) way, as requested in that review. I also
need it to be able to support "host" file systems as a content provider, see
bug 293678.

This patch also enforces that the "branch" of a channel is a string, and fixes a
bunch of callers, because a bug there was exposed as part of this work.

BUG= 273105, 293678
R=jyasskin@chromium.org

Review URL: https://codereview.chromium.org/26418002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227602 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227602