Parameterized MixerTest to run both with and without field trial.

Parameterized MixerTest to run both with and without field trial.

This runs the full suite of tests with the AppListMixer field trial set
to both "default" and "Blended", for full coverage of both code paths.

Also, MixerTest.Basic now has different expectations in the "Blended"
case, because the mixing behaviour has (deliberately) changed.

BUG=487494
Committed: https://crrev.com/6f95ef81b802417d612a6f23dd1663190d5286e1
Cr-Commit-Position: refs/heads/master@{#329605}

[Matt Giuca, 2015-05-13 05:19:55]

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

[calamity, 2015-05-13 06:00:34]

lgtm.

Consider noting somewhere why some cases have vastly more results than others.

[Matt Giuca, 2015-05-13 06:35:12]

Done.

[Matt Giuca, 2015-05-13 07:13:18]

The CQ bit was checked by mgiuca@chromium.org

[Matt Giuca, 2015-05-13 07:13:18]

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/1128683005/#ps20001
(title: "Added comment about test expectations.")

[commit-bot: I haz the power, 2015-05-13 07:13:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1128683005/20001

[commit-bot: I haz the power, 2015-05-13 07:58:10]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-13 08:00:05]

Patchset 2 (id:??) landed as
https://crrev.com/6f95ef81b802417d612a6f23dd1663190d5286e1
Cr-Commit-Position: refs/heads/master@{#329605}