Poll CanPredictNetworkActions in Predictor class.

Predictor is modified to call functions CanPredictNetworkActionsIO and
CanPredictNetworkActionsUI to comply with user preferences (and consider
network connection state).  This obsoletes Predictor::EnablePredictor.  Also,
bool members Predictor::preconnect_enabled_ and Predictor::predictor_enabled_
now depend solely on command line switches, therefore they are made const.

BUG=334602

Review URL: https://codereview.chromium.org/360733005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284526 0039d316-1c4b-4281-b951-d872f2087c98
8 files changed