Make CSSOM style() return CSSStyleDeclaration*

Make CSSOM style() return CSSStyleDeclaration*
https://bugs.webkit.org/show_bug.cgi?id=77475

Reviewed by Anders Carlsson

CSSStyleRule::style() and some other places return CSSMutableStyleDeclaration.
They should return the plain CSSOM type instead.

CSSMutableStyleDeclaration* should be available through non-CSSOM function.

* css/CSSFontFaceRule.h:
(WebCore::CSSFontFaceRule::style):
(WebCore::CSSFontFaceRule::declaration):
* css/CSSFontSelector.cpp:
(WebCore::CSSFontSelector::addFontFaceRule):
* css/CSSStyleRule.h:
(WebCore::CSSStyleRule::style):
(WebCore::CSSStyleRule::declaration):
* css/CSSStyleSelector.cpp:
(WebCore::CSSStyleSelector::styleForKeyframe):
* css/WebKitCSSKeyframeRule.h:
(WebCore):
(WebCore::WebKitCSSKeyframeRule::style):
(WebCore::WebKitCSSKeyframeRule::declaration):
(WebKitCSSKeyframeRule):
* editing/EditingStyle.cpp:
(WebCore::styleFromMatchedRulesForElement):
* inspector/InspectorStyleSheet.cpp:
(WebCore::InspectorStyleSheet::revalidateStyle):
* page/PageSerializer.cpp:
(WebCore::PageSerializer::retrieveResourcesForCSSRule):
* svg/SVGFontFaceElement.cpp:
(WebCore::SVGFontFaceElement::parseMappedAttribute):
(WebCore::SVGFontFaceElement::fontFamily):
(WebCore::SVGFontFaceElement::rebuildFontFace):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@106393 268f45cc-cd09-0410-ab3c-d52691b4dbfc