Fixing an alpha bug regression. If there are lists of selectors in a single rule the parser returns a shared instance of StyleDeclaration for each, so while the properties need to be processed in a shared manner, the selector and subject need to be unique. This change adds a shallowCopy to StyleDeclaration.
Reviewer: Darrell, Gaurav
SDK-17740 - [Advanced CSS] Type selectors using commas no longer work.