StorageAreaProxy should hold on to a StorageMap and not a HashMap
https://bugs.webkit.org/show_bug.cgi?id=110919

Reviewed by Jessie Berlin.

Source/WebCore:

StorageMap should be a private header.

* WebCore.xcodeproj/project.pbxproj:

Source/WebKit2:

Create a storage map instead of a hash map.

* WebProcess/Storage/StorageAreaProxy.cpp:
(WebKit::StorageAreaProxy::length):
(WebKit::StorageAreaProxy::loadValuesIfNeeded):
* WebProcess/Storage/StorageAreaProxy.h:
(WebCore):
(StorageAreaProxy):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144117 268f45cc-cd09-0410-ab3c-d52691b4dbfc