UI process storage areas should hold on to storage maps
https://bugs.webkit.org/show_bug.cgi?id=111374

Reviewed by Beth Dakin.

Pass the session storage quota size through to the storage area constructor and
create a StorageMap with the given quota size.

* UIProcess/Storage/StorageManager.cpp:
(StorageManager::StorageArea):
(WebKit::StorageManager::StorageArea::create):
(WebKit::StorageManager::StorageArea::StorageArea):
(StorageManager::SessionStorageNamespace):
(WebKit::StorageManager::SessionStorageNamespace::create):
(WebKit::StorageManager::SessionStorageNamespace::SessionStorageNamespace):
(WebKit::StorageManager::SessionStorageNamespace::getOrCreateStorageArea):
(WebKit::StorageManager::createSessionStorageNamespace):
(WebKit::StorageManager::createSessionStorageNamespaceInternal):
* UIProcess/Storage/StorageManager.h:
(StorageManager):
* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::WebPageProxy):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144695 268f45cc-cd09-0410-ab3c-d52691b4dbfc