Rename/tweak some StylePropertySet/CSSStyleDeclaration copying functions.

Rename/tweak some StylePropertySet/CSSStyleDeclaration copying functions.

- StylePropertySet::copy() -> mutableCopy() : This function now returns a MutableStylePropertySet,
and this is also reflected in the name.

- CSSStyleDeclaration::copy() -> copyProperties() : Renamed to reflect that it's the properties
being copied, not the CSSStyleDeclaration. They also now return MutableStylePropertySets.

- StylePropertySet::copyPropertiesInSet() and CSSStyleDeclaration::copyPropertiesInSet() :
These functions now return MutableStylePropertySets.

This is a backport from WebKit r148365. Patch by Andreas Kling and reviewed by Anders Carlsson.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=150925

[eseidel, 2013-05-22 19:36:46]

lgtm

Thanks!

[commit-bot: I haz the power, 2013-05-22 19:36:51]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/alexis.menard@intel.com/15746004/1

[commit-bot: I haz the power, 2013-05-22 21:02:42]

Change committed as 150925