EditingStyle should have a MutableStylePropertySet internally.
<http://webkit.org/b/114588>

Reviewed by Anders Carlsson.

Switch EditingStyle::m_mutableStyle to a RefPtr<MutableStylePropertySet>.

* css/StylePropertySet.cpp:
(WebCore::StylePropertySet::copyBlockProperties):
* css/StylePropertySet.h:
(StylePropertySet):
* editing/EditingStyle.cpp:
(WebCore::EditingStyle::setStyle):
(WebCore::EditingStyle::mergeStyleFromRules):
(WebCore::StyleChange::StyleChange):
(WebCore::setTextDecorationProperty):
(WebCore::StyleChange::extractTextStyles):
(WebCore::diffTextDecorations):
(WebCore::getPropertiesNotIn):
* editing/EditingStyle.h:
(WebCore::EditingStyle::style):
(EditingStyle):
(StyleChange):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148402 268f45cc-cd09-0410-ab3c-d52691b4dbfc