Merge latest MB from trunk back to M46.

Merge latest MB from trunk back to M46.

In order to be able to build the official linux x64 builds with GN
on trunk and GYP on the branches, we need to have the latest version
of MB on the branches for consistency (so that we can flip configs
without having to worry about not having all of the needful bug fixes
on the branch).

R=kerz@chromium.org
BUG=530733
Committed: https://chromium.googlesource.com/chromium/src/+/0ec4c0e4978531d88f9fc903f4d82203d6fb3b28

[Dirk Pranke, 2015-09-26 00:39:23]

This is a straight copy of src/tools/mb@{#350953}. It picks up all of the
bugfixes and changes between the branch point and now.

I feel better with this approach even though it's a bigger patch than is
strictly needed; if you'd rather me spend the time to try and come up with a
smaller patch, let me know.

[Dirk Pranke, 2015-09-26 00:40:00]

On 2015/09/26 00:39:23, Dirk Pranke wrote:
> This is a straight copy of src/tools/mb@{#350953}. It picks up all of the
> bugfixes and changes between the branch point and now.
> 
> I feel better with this approach even though it's a bigger patch than is
> strictly needed; if you'd rather me spend the time to try and come up with a
> smaller patch, let me know.

(Probably we only really need a tiny subset of the changes in mb_config.pyl).

[kerz_chromium, 2015-09-26 03:10:53]

lgtm

I think it's fine.

[kerz_chromium, 2015-09-26 03:11:03]

lgtm

[Dirk Pranke, 2015-09-28 18:30:39]

Committed patchset #1 (id:1) manually as
0ec4c0e4978531d88f9fc903f4d82203d6fb3b28 (tree was closed).