DevTools: rename test resource file blink-fs.js into less confusing name

Rename blink-fs.js into example-fileset-for-test.js

BUG=

Review URL: https://codereview.chromium.org/151353003

git-svn-id: svn://svn.chromium.org/blink/trunk@166308 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Implement DOMWrapperWorlds for workers

Currently we have DOMWrapperWorlds for a main world and isolated worlds
but don't have DOMWrapperWorlds for worker worlds.

This design is inconsistent and causes a couple of mess in V8 binding.
For example, we have to be careful that we're in the main thread when
calling DOMWrapperWorld::current() (since workers don't have DOMWrapperWorlds).

We should implement DOMWrapperWorld for worker worlds as well, so that
we can treat all worlds consistently.

(Note: This change is necessary for inserting assertions to ScopedPersistent
to verify that ScopedPersistent doesn't leak between worlds.)

BUG=339800
TBR=abarth (for web/)

Review URL: https://codereview.chromium.org/151443002

git-svn-id: svn://svn.chromium.org/blink/trunk@166309 bbb929c8-8fbe-4397-9dbb-9b2b20218538