Make sure ImmutableStylePropertySet uses the new 16 bits size of StylePropertyMetadata.

Source/core/css/CSSProperty.h

Index: Source/core/css/CSSProperty.h
diff --git a/Source/core/css/CSSProperty.h b/Source/core/css/CSSProperty.h
index 7b12f9bd1febe05c4fa3cf7e8cec3326fe41a28a..82be79c8d1d7460e73571203736dc68bf226307a 100644
--- a/Source/core/css/CSSProperty.h
+++ b/Source/core/css/CSSProperty.h
@@ -41,6 +41,11 @@ struct StylePropertyMetadata {
     {
     }
 
+    StylePropertyMetadata(uint32_t data)
+    {
+        memcpy(this, &data, sizeof(StylePropertyMetadata));

[Jeffrey Yasskin, 2013/06/21 19:56:27]

memcpy is dangerous because of endian-ness issues, so either be sure to test
this on a big-endian machine (to be sure that data is always an in-memory value)
or do the shifting yourself in this constructor.

+    }
+
     CSSPropertyID shorthandID() const;
 
     unsigned m_propertyID : 10;

[Jeffrey Yasskin, 2013/06/21 19:56:27]

If you change the type of these fields to uint16_t, that should reduce
sizeof(StylePropertyMetadata) to 2 on x86, and probably on all 8-bit-byte
architectures. (Inferring from "bit-fields must be contained in a storage unit
appropriate for its declared type" in the AMD64 ABI v0.99, which I can't find on
the internet anymore. :( )

This probably obviates the rest of the CL, but I've left my C++-correctness
comments anyway.