CSSValue Immediates: Add move operators to CSSValue and NullableCSSValue

Source/core/css/CSSValue.h

Index: Source/core/css/CSSValue.h
diff --git a/Source/core/css/CSSValue.h b/Source/core/css/CSSValue.h
index 609dcbc85afcae15a768dc5b5debdca568aa6112..28a560cbf2577f6e2fa604c60db5b89e25c0236b 100644
--- a/Source/core/css/CSSValue.h
+++ b/Source/core/css/CSSValue.h
@@ -69,7 +69,10 @@ public:
 
     ~CSSValue()
     {
-        deref();
+        // Although m_data can't be null, a move constructor from NullableCSSValue
+        // could make it null for a short time.
+        if (m_data)
+            deref();
     }
 
     CSSValue& operator=(const CSSValue& rhs)
@@ -80,6 +83,18 @@ public:
         return *this;
     }
 
+    CSSValue& operator=(CSSValue&& rhs)
+    {
+        m_data = rhs.m_data;
+        rhs.m_data.clear();
+        return *this;
+    }
+
+    CSSValue(CSSValue&& rhs)
+    {
+        m_data = rhs.m_data;
+    }
+
     bool operator==(const CSSValue& other) const
     {
         return m_data->equals(*other.m_data);
@@ -231,6 +246,12 @@ public:
         return m_data;
     }
 
+    NullableCSSValue(NullableCSSValue&& rhs)
+    {
+        m_data = rhs.m_data;
+        rhs.m_data = nullptr;
+    }
+
     NullableCSSValue& operator=(const NullableCSSValue& rhs)
     {
         rhs.ref();
@@ -239,7 +260,14 @@ public:
         return *this;
     }
 
-    bool operator==(const NullableCSSValue& rhs)
+    NullableCSSValue& operator=(NullableCSSValue&& rhs)
+    {
+        m_data = rhs.m_data;
+        rhs.m_data.clear();
+        return *this;
+    }
+
+    bool operator==(const NullableCSSValue& rhs) const
     {
         return m_data ? rhs.m_data && m_data->equals(*rhs.m_data) : !bool(rhs.m_data);
     }