Add a temporary variable to store ANGLE gyp file.

Add a temporary variable to store ANGLE gyp file.

This will allow us to correctly transition to the new angle.gypi
from the old build_angle.gypi.

BUG=415893
Committed: https://crrev.com/90d07e614c526dd382e7dbb64732a73781b31af3
Cr-Commit-Position: refs/heads/master@{#297017}

[Jamie Madill, 2014-09-26 18:41:57]

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

[Jamie Madill, 2014-09-26 18:42:16]

PTAL Brett, re our conversation about updating the angle gyp filename.

[brettw, 2014-09-26 19:20:33]

lgtm

[Jamie Madill, 2014-09-26 20:03:31]

The CQ bit was checked by jmadill@chromium.org

[commit-bot: I haz the power, 2014-09-26 20:04:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/604413002/1

[commit-bot: I haz the power, 2014-09-26 20:09:34]

Committed patchset #1 (id:1) as db7f633cabc9abfea8815ae84678c18800c3022d

[commit-bot: I haz the power, 2014-09-26 20:10:14]

Patchset 1 (id:??) landed as
https://crrev.com/90d07e614c526dd382e7dbb64732a73781b31af3
Cr-Commit-Position: refs/heads/master@{#297017}