Move Worker-related APIs from DOMWindow.idl to DOMWindowWorker.idl

Move Worker-related APIs from DOMWindow.idl to DOMWindowWorker.idl
https://bugs.webkit.org/show_bug.cgi?id=79442

Reviewed by Adam Barth.

For WebKit modularization, this patch moves Worker-related APIs
from DOMWindow.idl to DOMWindowWorker.idl.

No tests. No change in behavior.

* workers/DOMWindowWorker.idl: Added.
* page/DOMWindow.idl:

* CMakeLists.txt:
* DerivedSources.make:
* DerivedSources.pri:
* GNUmakefile.list.am:
* WebCore.gypi:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108778 268f45cc-cd09-0410-ab3c-d52691b4dbfc