add flag to guard new miplevel code

add flag to guard new miplevel code

for skia change https://codereview.chromium.org/1131613002/

BUG=
NOTRY=True
win failure unrelated to this CL

Committed: https://crrev.com/d7c41c74cd78f5da5eea8a31c52ce3e587e28750
Cr-Commit-Position: refs/heads/master@{#328590}

[reed1, 2015-05-06 17:36:38]

reed@google.com changed reviewers:
+ robertphillips@chromium.org

[reed1, 2015-05-06 17:36:43]

The CQ bit was checked by reed@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-05-06 17:37:11]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1131663002/1

[robertphillips, 2015-05-06 17:37:17]

robertphillips@google.com changed reviewers:
+ robertphillips@google.com

[robertphillips, 2015-05-06 17:37:18]

lgtm

[reed1, 2015-05-06 18:07:46]

The CQ bit was unchecked by reed@google.com

[reed1, 2015-05-06 18:07:54]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2015-05-06 18:08:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1131663002/1

[reed1, 2015-05-06 19:48:29]

The CQ bit was unchecked by reed@google.com

[reed1, 2015-05-06 19:48:50]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2015-05-06 19:50:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1131663002/1

[commit-bot: I haz the power, 2015-05-06 19:56:27]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-06 19:58:29]

Patchset 1 (id:??) landed as
https://crrev.com/d7c41c74cd78f5da5eea8a31c52ce3e587e28750
Cr-Commit-Position: refs/heads/master@{#328590}