Minor refactor to support experiments in AppListMixer.

Minor refactor to support experiments in AppListMixer.

Removed the concept of max_results == 0 meaning "unlimited" in mixer
groups. Now, the omnibox group is specifically considered unlimited (and
all other groups have a defined maximum).

BUG=487494
Committed: https://crrev.com/2579eba5109325886654cef3a87b96f7ba90434d
Cr-Commit-Position: refs/heads/master@{#329590}

[Matt Giuca, 2015-05-13 02:19:31]

mgiuca@chromium.org changed reviewers:
+ calamity@chromium.org

[calamity, 2015-05-13 03:14:30]

lgtm

[Matt Giuca, 2015-05-13 03:15:07]

The CQ bit was checked by mgiuca@chromium.org

[commit-bot: I haz the power, 2015-05-13 03:15:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1139493004/20001

[commit-bot: I haz the power, 2015-05-13 03:41:24]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-05-13 03:41:26]

Try jobs failed on following builders:
  mac_chromium_compile_dbg_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)

[Matt Giuca, 2015-05-13 04:22:06]

The CQ bit was checked by mgiuca@chromium.org

[Matt Giuca, 2015-05-13 04:22:07]

The patchset sent to the CQ was uploaded after l-g-t-m from
calamity@chromium.org
Link to the patchset: https://codereview.chromium.org/1139493004/#ps40001
(title: "Fix compile.")

[commit-bot: I haz the power, 2015-05-13 04:22:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1139493004/40001

[commit-bot: I haz the power, 2015-05-13 05:18:19]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-05-13 05:19:14]

Patchset 3 (id:??) landed as
https://crrev.com/2579eba5109325886654cef3a87b96f7ba90434d
Cr-Commit-Position: refs/heads/master@{#329590}