[EFL] NetworkStateNotifier::updateState() is called too often

[EFL] NetworkStateNotifier::updateState() is called too often
https://bugs.webkit.org/show_bug.cgi?id=113152

Reviewed by Kenneth Rohde Christiansen.

Wait until we have read all the data on the Netlink socket before
reporting a possible network interface change. This way, we make
sure we don't call NetworkStateNotifier::updateState() several
times in a row for no reason.

We also call NetworkStateNotifier::updateState() only if we get a
RTM_NEWADDR event and we are currently offline, or if we get a
RTM_DELADDR and we are currently online. This avoids calling
NetworkStateNotifier::updateState() uselessly as there is no way
the online state can change otherwise.

No new tests, no behavior change for layout tests.

* platform/network/efl/NetworkStateNotifierEfl.cpp:
(WebCore::NetworkStateNotifier::readSocketCallback):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@146728 268f45cc-cd09-0410-ab3c-d52691b4dbfc