Move PropertySetCSSStyleDeclaration to a file of its own

Move PropertySetCSSStyleDeclaration to a file of its own
https://bugs.webkit.org/show_bug.cgi?id=79121

Rubber-stamped by Andreas Kling.

This makes StylePropertySet.cpp more readable.

* CMakeLists.txt:
* GNUmakefile.list.am:
* Target.pri:
* WebCore.gypi:
* WebCore.vcproj/WebCore.vcproj:
* WebCore.xcodeproj/project.pbxproj:
* css/PropertySetCSSStyleDeclaration.cpp: Copied from Source/WebCore/css/StylePropertySet.cpp.
(WebCore::PropertySetCSSStyleDeclaration::ref):
(WebCore::PropertySetCSSStyleDeclaration::deref):
(WebCore):
* css/PropertySetCSSStyleDeclaration.h: Added.
(WebCore):
(PropertySetCSSStyleDeclaration):
(WebCore::PropertySetCSSStyleDeclaration::PropertySetCSSStyleDeclaration):
(WebCore::PropertySetCSSStyleDeclaration::parentElement):
(WebCore::PropertySetCSSStyleDeclaration::clearParentRule):
(WebCore::PropertySetCSSStyleDeclaration::clearParentElement):
(WebCore::PropertySetCSSStyleDeclaration::contextStyleSheet):
(WebCore::PropertySetCSSStyleDeclaration::setNeedsStyleRecalc):
(RuleCSSStyleDeclaration):
(WebCore::RuleCSSStyleDeclaration::RuleCSSStyleDeclaration):
(WebCore::RuleCSSStyleDeclaration::parentRule):
(WebCore::RuleCSSStyleDeclaration::clearParentRule):
(InlineCSSStyleDeclaration):
(WebCore::InlineCSSStyleDeclaration::InlineCSSStyleDeclaration):
(WebCore::InlineCSSStyleDeclaration::parentElement):
(WebCore::InlineCSSStyleDeclaration::clearParentElement):
* css/StylePropertySet.cpp:
(WebCore):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108370 268f45cc-cd09-0410-ab3c-d52691b4dbfc