Remove TestNetworkPredictionEnabledPref.

Remove TestNetworkPredictionEnabledPref.

TestNetworkPredictionEnabledPref is a quite useless test: it verifies that a
preference is at its default value, then essentialy checks that PrefService
accessors work.  This is not what the test was meant to test for, see
comments in https://chromiumcodereview.appspot.com/21432002/diff/1/chrome/browser/prefs/pref_functional_browsertest.cc
for the original discussion.  Can we please just get rid of this test?

The first patch shows how I whould have proposed to update the test to use
kNetworkPredictionOptions instead of the obsolete kNetworkPredictionEnabled,
if the test had needed to stay.

BUG=334602
Committed: https://crrev.com/a75ca453dc5b2c05e8a2a616c9e00227fd3ab766
Cr-Commit-Position: refs/heads/master@{#299474}

[Bence, 2014-10-13 18:47:36]

bnc@chromium.org changed reviewers:
+ battre@chromium.org

[Bence, 2014-10-13 18:47:37]

PTAL.  Thank you.

[battre, 2014-10-14 07:19:35]

Feel free to just remove this test.

[Bence, 2014-10-14 13:51:12]

PTAL.

[battre, 2014-10-14 14:02:06]

The CQ bit was checked by battre@chromium.org

[battre, 2014-10-14 14:02:06]

lgtm

[commit-bot: I haz the power, 2014-10-14 14:02:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/648293002/130001

[commit-bot: I haz the power, 2014-10-14 14:12:47]

Committed patchset #2 (id:130001)

[commit-bot: I haz the power, 2014-10-14 14:13:36]

Patchset 2 (id:??) landed as
https://crrev.com/a75ca453dc5b2c05e8a2a616c9e00227fd3ab766
Cr-Commit-Position: refs/heads/master@{#299474}