[Refactoring] rename StyleRuleBlock -> StyleRuleGroup

[Refactoring] rename StyleRuleBlock -> StyleRuleGroup
https://bugs.webkit.org/show_bug.cgi?id=107415

Reviewed by Antti Koivisto.

StyleRuleBlock should be renamed StyleRuleGroup, because
CSSGroupingRule (not CSSBlockRule) is an interface for an at-rule that
contains other rules nested inside itself:
http://www.w3.org/TR/2012/WD-css3-conditional-20121213/#the-cssgroupingrule-interface
To match the name: CSSGroupingRule, StyleRuleGroup looks better.

No new tests, because just refactoring.

* css/CSSGroupingRule.cpp:
(WebCore::CSSGroupingRule::CSSGroupingRule):
(WebCore::CSSGroupingRule::reattach):
* css/CSSGroupingRule.h:
(CSSGroupingRule):
* css/StyleRule.cpp:
(WebCore::StyleRuleGroup::StyleRuleGroup):
(WebCore::StyleRuleGroup::wrapperInsertRule):
(WebCore::StyleRuleGroup::wrapperRemoveRule):
(WebCore::StyleRuleGroup::reportDescendantMemoryUsage):
(WebCore::StyleRuleMedia::StyleRuleMedia):
(WebCore::StyleRuleSupports::StyleRuleSupports):
(WebCore::StyleRuleRegion::StyleRuleRegion):
* css/StyleRule.h:
(StyleRuleGroup):
(WebCore::StyleRuleHost::StyleRuleHost):
(WebCore::toStyleRuleMedia):
(WebCore::toStyleRuleSupports):
(WebCore::toStyleRuleRegion):
Just replaced StyleRuleBlock with StyleRuleGroup.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@140316 268f45cc-cd09-0410-ab3c-d52691b4dbfc