Oilpan: NetworkInformation should be RefCountedGarbageCollected

This CL just moves NetworkInformation from RefCounted to RefCountedGarbageCollected.
I tried to ship Oilpan for netinfo/ but realized that there is nothing we can do at this point
because all objects in netinfo/ inherit from EventTarget or WillBeHeapSupplement.

BUG=340522

Review URL: https://codereview.chromium.org/496643002

git-svn-id: svn://svn.chromium.org/blink/trunk@180702 bbb929c8-8fbe-4397-9dbb-9b2b20218538