https://bugs.webkit.org/show_bug.cgi?id=94926

Reviewed by Andreas Kling.

To be able to cache and share @imported stylesheets in the future there must not be any parent
pointers in the stylesheet tree.

Parent pointers are used during loading to invoke load completion callbacks and for
accessing document context information (like the security origin). They are not used after
the sheet load is complete. Instead of keeping the parent pointers around indefinitely as part of the 
stylesheet data structure we just keep a pointer to the root CSSStyleSheet for the duration of the load.
        
This patch doesn't enable any new caching or generally change the behavior.

* css/CSSStyleSheet.cpp:
(WebCore::CSSStyleSheet::insertRule):
(WebCore::CSSStyleSheet::rootStyleSheet):
(WebCore):
(WebCore::CSSStyleSheet::ownerDocument):
* css/CSSStyleSheet.h:
(CSSStyleSheet):
* css/StyleRuleImport.cpp:
(WebCore::StyleRuleImport::LoadContext::LoadContext):
        
    Simplify by making StyleRuleImport CachedStyleSheetClient directly. LoadContext contains
    fields that can be thrown away after load completes.

(WebCore):
(WebCore::StyleRuleImport::StyleRuleImport):
(WebCore::StyleRuleImport::~StyleRuleImport):
(WebCore::StyleRuleImport::setCSSStyleSheet):
(WebCore::StyleRuleImport::isLoading):
(WebCore::StyleRuleImport::hadLoadError):
(WebCore::StyleRuleImport::requestStyleSheet):
* css/StyleRuleImport.h:
(StyleRuleImport):
(LoadContext):
* css/StyleSheetContents.cpp:
(WebCore::StyleSheetContents::StyleSheetContents):
        
    Remove now unnecessary constructor. 

(WebCore::StyleSheetContents::isCacheable):
(WebCore::StyleSheetContents::parserAppendRule):
(WebCore::StyleSheetContents::clearRules):
(WebCore::StyleSheetContents::wrapperInsertRule):
(WebCore::StyleSheetContents::wrapperDeleteRule):
(WebCore::StyleSheetContents::requestImportedStyleSheets):
(WebCore):
(WebCore::StyleSheetContents::parseAuthorStyleSheet):
(WebCore::StyleSheetContents::parseStringAtLine):
(WebCore::StyleSheetContents::checkImportedSheetLoadCompleted):
(WebCore::StyleSheetContents::checkLoadCompleted):
(WebCore::StyleSheetContents::getAncestors):
(WebCore::StyleSheetContents::hasImportCycle):
        
    Move the cycle checking to the root stylesheet so we don't need to pass the entire chain around.
    The extra work here is unlikely to cause problems, massive import trees don't really occur in
    practice.

* css/StyleSheetContents.h:
(WebCore::StyleSheetContents::create):
(StyleSheetContents):
* dom/ProcessingInstruction.cpp:
(WebCore::ProcessingInstruction::parseStyleSheet):
* dom/StyleElement.cpp:
(WebCore::StyleElement::createSheet):
* html/HTMLLinkElement.cpp:
(WebCore::HTMLLinkElement::setCSSStyleSheet):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@126717 268f45cc-cd09-0410-ab3c-d52691b4dbfc