Revert 132288 - Shrink immutable ElementAttributeData and StylePropertySet by one pointer each.

Revert 132288 - Shrink immutable ElementAttributeData and StylePropertySet by one pointer each.
<http://webkit.org/b/100123>;

Reviewed by Anders Carlsson.

Remove one pointer of unintentional padding in the immutable versions of these objects.
583kB progression on Membuster3.

* css/StylePropertySet.cpp:
(WebCore::immutableStylePropertySetSize):
* dom/ElementAttributeData.cpp:
(WebCore::immutableElementAttributeDataSize):


TBR=kling@webkit.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=132559