Use the page group id from the UI process as the local storage namespace ID
https://bugs.webkit.org/show_bug.cgi?id=114836

Reviewed by Beth Dakin.

The WebCore PageGroup identifier is different across processes, so use the one given to us by the UI process.

* WebProcess/Storage/StorageNamespaceImpl.cpp:
(WebKit::StorageNamespaceImpl::createLocalStorageNamespace):
* WebProcess/WebPage/WebPageGroupProxy.h:
(WebKit::WebPageGroupProxy::corePageGroup):
* WebProcess/WebProcess.cpp:
(WebKit::WebProcess::webPageGroup):
* WebProcess/WebProcess.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148715 268f45cc-cd09-0410-ab3c-d52691b4dbfc