Implement more StorageAreaProxy member functions
https://bugs.webkit.org/show_bug.cgi?id=111103

Reviewed by Sam Weinig.

Source/WebCore:

Export two more StorageMap symbols required by WebKit2.

* WebCore.exp.in:

Source/WebKit2:

* Shared/SecurityOriginData.cpp:
(WebKit::SecurityOriginData::securityOrigin):
* Shared/SecurityOriginData.h:
Add helper to create a WebCore::SecurityOrigin from a SecurityOriginData object.

* WebProcess/Storage/StorageAreaProxy.cpp:
(WebKit::StorageAreaProxy::key):
Fill the storage map and call through to StorageMap::key.

(WebKit::StorageAreaProxy::contains):
Fill the storage map and call through to StorageMap::contains.

(WebKit::StorageAreaProxy::memoryBytesUsedByCache):
Return 0; this matches StorageAreaImpl.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144351 268f45cc-cd09-0410-ab3c-d52691b4dbfc