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.

Review URL: https://chromiumcodereview.appspot.com/15746004

git-svn-id: svn://svn.chromium.org/blink/trunk@150925 bbb929c8-8fbe-4397-9dbb-9b2b20218538
15 files changed