Fix a crash for extractSmartClipData

Position::document() returns null if -webkit-user-select is set to none.
This CL prevents the crash in this case. Also adds a test to make sure
that the crash does not happen and clip text and clip html are empty.

TEST=passed WebViewTest
BUG=402371

Review URL: https://codereview.chromium.org/455133003

git-svn-id: svn://svn.chromium.org/blink/trunk@180701 bbb929c8-8fbe-4397-9dbb-9b2b20218538
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
Add support for CallbackPromiseAdapter<void, T> matching WebCallbacks<void, T>.

This makes it possible to eliminate the various UndefinedValue classes that are sprinkled throughout the Service Worker code.

Review URL: https://codereview.chromium.org/468913007

git-svn-id: svn://svn.chromium.org/blink/trunk@180703 bbb929c8-8fbe-4397-9dbb-9b2b20218538