Reviewed by MitzPettel

        <rdar://problem/6078543> - Many LocalStorageThreads may be started

        The original decision to key LocalStorage sets to PageGroups was a poor one.

        It seems a much better solution is to key them to the actual path of on-disk storage,
        which also solves all of the avenues that could lead to a boundless number of threads.

        In this patch, I am not attempting to completely sever the attachment of LocalStorage
        to PageGroups as that would require a more substantial re-working of the lifetime
        between pages, groups, and local storage threads.

        * page/PageGroup.cpp:
        (WebCore::PageGroup::addPage):

        * storage/LocalStorage.cpp:
        (WebCore::localStorageMap):  Map paths to LocalStorage objects here.
        (WebCore::LocalStorage::localStorage): Return the shared LocalStorage object for this path,
          or create a new one if it doesn't yet exist.
        (WebCore::LocalStorage::LocalStorage):
        (WebCore::LocalStorage::~LocalStorage):  Add to remove the path->LocalStorage mapping
        * storage/LocalStorage.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@35614 268f45cc-cd09-0410-ab3c-d52691b4dbfc