Add a move constructor and move assignment operator to Length

Source/platform/Length.h

 /*
     Copyright (C) 1999 Lars Knoll (knoll@kde.org)
     Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
     Copyright (C) 2011 Rik Cabanier (cabanier@adobe.com)
     Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
     version 2 of the License, or (at your option) any later version.
@@ skipping 102 matching lines @@
     Length& operator=(const Length& length)
     {
         if (length.isCalculated())
             length.incrementCalculatedRef();
         if (isCalculated())
             decrementCalculatedRef();
         memcpy(this, &length, sizeof(Length));
         return *this;
     }
 
+#if COMPILER_SUPPORTS(CXX_RVALUE_REFERENCES)
+    Length(Length&& length)
+    {
+        memcpy(this, &length, sizeof(Length));
+        length.m_type = Auto;

[tkent, 2014/05/27 00:13:29]

Why do we need do length.m_type=Auto though |length| is rvalue?

[Inactive, 2014/05/27 00:33:29]

We basically want to make sure that |length|'s destructor won't call
decrementCalculatedRef() (as isCalculated() check will fail) since we don't call
length.incrementCalculatedRef() here.

+    }
+
+    Length& operator=(Length&& length)
+    {
+        if (this == &length)
+            return *this;
+
+        if (isCalculated())
+            decrementCalculatedRef();
+
+        memcpy(this, &length, sizeof(Length));
+        length.m_type = Auto;

[tkent, 2014/05/27 00:13:29]

Ditto.

I understand length.incrementCalculatedRef() is unnecessary in this case.

+        return *this;
+    }
+#endif
+
     ~Length()
     {
         if (isCalculated())
             decrementCalculatedRef();
     }
 
     bool operator==(const Length& o) const { return (m_type == o.m_type) && (m_quirk == o.m_quirk) && (isUndefined() || (getFloatValue() == o.getFloatValue()) || isCalculatedEqual(o)); }
     bool operator!=(const Length& o) const { return !(*this == o); }
 
     const Length& operator*=(float v)
@@ skipping 185 matching lines @@
     bool m_quirk;
     unsigned char m_type;
     bool m_isFloat;
 };
 
 PLATFORM_EXPORT Vector<Length> parseHTMLAreaElementCoords(const String&);
 
 } // namespace WebCore
 
 #endif // Length_h