Use a response file for gn refs when running 'analyze' on gn bots.

Use a response file for gn refs when running 'analyze' on gn bots.

Previously we would invoke 'gn refs' once for each file modified in
a CL; this was terribly inefficient. Switching to a response file
makes things run much faster. This is a precursor to fixing
the actual problem in bug 487035, because we will be doubling the
number of times we need to call gn refs in the fix.

R=scottmg@chromium.org
BUG=487035
CQ_EXTRA_TRYBOTS=tryserver.chromium.mac:mac_chromium_gn_rel;tryserver.chromium.win:win8_chromium_gn_rel

Committed: https://crrev.com/f61de2f16ff7264dd9463d1978fb6acff598285f
Cr-Commit-Position: refs/heads/master@{#329799}

[Dirk Pranke, 2015-05-13 23:30:18]

dpranke@chromium.org changed reviewers:
+ brettw@chromium.org

[Dirk Pranke, 2015-05-13 23:30:19]

See also https://codereview.chromium.org/1098603002 for the gn-side change that
implemented the response files (landed a month ago but we haven't been using
it).

[Dirk Pranke, 2015-05-13 23:38:56]

The CQ bit was checked by dpranke@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-05-13 23:41:22]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1131623006/1

[scottmg, 2015-05-13 23:57:26]

lgtm

https://codereview.chromium.org/1131623006/diff/1/tools/mb/mb_unittest.py
File tools/mb/mb_unittest.py (right):

https://codereview.chromium.org/1131623006/diff/1/tools/mb/mb_unittest.py#new...
tools/mb/mb_unittest.py:67: self.files[self.name] = self.buf
wrong indent

https://codereview.chromium.org/1131623006/diff/1/tools/mb/mb_unittest.py#new...
tools/mb/mb_unittest.py:68: 
nit; extra \n

[Dirk Pranke, 2015-05-14 00:11:23]

The CQ bit was checked by dpranke@chromium.org

[Dirk Pranke, 2015-05-14 00:11:24]

The patchset sent to the CQ was uploaded after l-g-t-m from scottmg@chromium.org
Link to the patchset: https://codereview.chromium.org/1131623006/#ps20001
(title: "fix formatting nits")

[commit-bot: I haz the power, 2015-05-14 00:13:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1131623006/20001

[commit-bot: I haz the power, 2015-05-14 04:10:02]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-14 04:10:48]

Patchset 2 (id:??) landed as
https://crrev.com/f61de2f16ff7264dd9463d1978fb6acff598285f
Cr-Commit-Position: refs/heads/master@{#329799}