Move StyleSheetContents cache to StyleEngine.

Source/core/css/CSSStyleSheet.cpp

Index: Source/core/css/CSSStyleSheet.cpp
diff --git a/Source/core/css/CSSStyleSheet.cpp b/Source/core/css/CSSStyleSheet.cpp
index d9f73c8f26764e1a654b3aa6a224d5d86310c998..88978e577c5efac65bc15463d1e6f05fbf83f6ef 100644
--- a/Source/core/css/CSSStyleSheet.cpp
+++ b/Source/core/css/CSSStyleSheet.cpp
@@ -158,11 +158,11 @@ CSSStyleSheet::~CSSStyleSheet()
 void CSSStyleSheet::willMutateRules()
 {
     InspectorInstrumentation::willMutateRules(this);
+
     // If we are the only client it is safe to mutate.
-    if (m_contents->hasOneClient() && !m_contents->isInMemoryCache()) {
+    if (m_contents->clientSize() <= 1 && !m_contents->isInMemoryCache()) {
         m_contents->clearRuleSet();
-        if (m_contents->maybeCacheable())
-            StyleEngine::removeSheet(m_contents.get());
+        m_contents->removeSheetFromCache(ownerDocument());
         m_contents->setMutable();
         return;
     }
@@ -183,7 +183,7 @@ void CSSStyleSheet::willMutateRules()
 void CSSStyleSheet::didMutateRules()
 {
     ASSERT(m_contents->isMutable());
-    ASSERT(m_contents->hasOneClient());
+    ASSERT(m_contents->clientSize() <= 1);
 
     InspectorInstrumentation::didMutateRules(this);
     didMutate(PartialRuleUpdate);
@@ -255,6 +255,14 @@ CSSRule* CSSStyleSheet::item(unsigned index)
     return cssRule.get();
 }
 
+void CSSStyleSheet::clearOwnerNode()
+{
+    didMutate(EntireStyleSheetUpdate);
+    if (m_ownerNode)
+        m_contents->unregisterClient(this);
+    m_ownerNode = 0;
+}
+
 bool CSSStyleSheet::canAccessRules() const
 {
     if (m_isInlineStylesheet)