Avoid parsing css text if there are identical inline style blocks.

Source/core/css/StyleSheetContents.h

Index: Source/core/css/StyleSheetContents.h
diff --git a/Source/core/css/StyleSheetContents.h b/Source/core/css/StyleSheetContents.h
index 184faaff1453748050892924ffbd913dc81a86a3..6d218b615e9c3a9e74fabf83e155dda87d276fd0 100644
--- a/Source/core/css/StyleSheetContents.h
+++ b/Source/core/css/StyleSheetContents.h
@@ -67,9 +67,11 @@ public:
     bool parseStringAtPosition(const String&, const TextPosition&, bool);
 
     bool isCacheable() const;
+    bool maybeCacheable() const;
 
     bool isLoading() const;
 
+    void checkLoadedFor(PassRefPtr<Node>);
     void checkLoaded();
     void startLoadingDynamicSheet();
 
@@ -86,7 +88,7 @@ public:
     KURL completeURL(const String& url) const;
     void addSubresourceStyleURLs(ListHashSet<KURL>&);
 
-    void setHasSyntacticallyValidCSSHeader(bool b) { m_hasSyntacticallyValidCSSHeader = b; }
+    void setHasSyntacticallyValidCSSHeader(bool isValidCss);
     bool hasSyntacticallyValidCSSHeader() const { return m_hasSyntacticallyValidCSSHeader; }
 
     void parserAddNamespace(const AtomicString& prefix, const AtomicString& uri);
@@ -131,7 +133,7 @@ public:
     bool hasOneClient() { return m_clients.size() == 1; }
 
     bool isMutable() const { return m_isMutable; }
-    void setMutable() { m_isMutable = true; }
+    void setMutable();
 
     bool isInMemoryCache() const { return m_isInMemoryCache; }
     void addedToMemoryCache();
@@ -144,6 +146,7 @@ private:
     StyleSheetContents(const StyleSheetContents&);
 
     void clearCharsetRule();
+    void clearCache();
 
     StyleRuleImport* m_ownerRule;