Clear mutable inline style when it is empty.

Source/core/css/VariablesIterator.h

Index: Source/core/css/VariablesIterator.h
diff --git a/Source/core/css/VariablesIterator.h b/Source/core/css/VariablesIterator.h
index de945948ec6db008aef720c1f973d0ed90ad3eb8..d151c131b88e5f3f7573d3ee10c1e72808add4e3 100644
--- a/Source/core/css/VariablesIterator.h
+++ b/Source/core/css/VariablesIterator.h
@@ -27,6 +27,7 @@
 namespace WebCore {
 
 class MutableStylePropertySet;
+class StylePropertySet;
 
 class AbstractVariablesIterator : public CSSVariablesIterator {
 public:
@@ -35,6 +36,8 @@ public:
 protected:
     void takeRemainingNames(Vector<AtomicString>& remainingNames) { m_remainingNames.swap(remainingNames); }
 
+    virtual void initRemainingNames(const StylePropertySet*);
+
 private:
     virtual void advance() OVERRIDE;
     virtual bool atEnd() const OVERRIDE { return m_remainingNames.isEmpty(); }
@@ -52,11 +55,9 @@ private:
 
 class VariablesIterator : public AbstractVariablesIterator {
 public:
-    static PassRefPtr<VariablesIterator> create(MutableStylePropertySet*);
+    explicit VariablesIterator(MutableStylePropertySet*);
 
 private:
-    explicit VariablesIterator(MutableStylePropertySet* propertySet) : m_propertySet(propertySet) { }
-
     virtual MutableStylePropertySet* propertySet() const OVERRIDE { return m_propertySet.get(); }
 
     RefPtr<MutableStylePropertySet> m_propertySet;