Implement layoutTestController.waitForPolicyDelegate on Windows

Implement layoutTestController.waitForPolicyDelegate on Windows

Fixes <http://webkit.org/b/25038> <rdar://problem/6790213>.

Reviewed by Simon Fraser.

LayoutTests:

Unskip tests that rely on layoutTestController.waitForPolicyDelegate on
Windows

* platform/win/Skipped:

WebKitTools:

* DumpRenderTree/win/LayoutTestControllerWin.cpp:
(LayoutTestController::waitForPolicyDelegate): Implemented by porting
code from LayoutTestControllerMac.mm.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@72311 268f45cc-cd09-0410-ab3c-d52691b4dbfc