MUST LAND AFTER crrev.com/302543006

Adds Netinfo v3 to Blink.

The layout changes outside of netinfo/ are regolding.

Design doc: https://docs.google.com/a/chromium.org/document/d/1LTk9uVMGi4kurzcF5ellsAJReTF31fFJMHrQwSVtBjc/

BUG=368358

Review URL: https://codereview.chromium.org/291203002

git-svn-id: svn://svn.chromium.org/blink/trunk@175200 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Oilpan: Reduce RefPtr to WorkerGlobalScope.

This CL reduces the number of required Heap::collectGarbage calls in
Heap::collectAllGarbage on Worker termination.

 - Make Event::m_target Member<>.
 - Make MessageEvent::m_source Member<>.
  MessageEvent is used to communicate between the main thread and workers.
  For consistency, this CL adjusts MessagePort argument/return types.

They reduce RefPtr to WorkerGlobalScope, which implements EventTarget.

BUG=375671

Review URL: https://codereview.chromium.org/304353004

git-svn-id: svn://svn.chromium.org/blink/trunk@175201 bbb929c8-8fbe-4397-9dbb-9b2b20218538