Rename default -> initial style and use singletons.

Rename default -> initial style and use singletons.

Default style is normally referred to the style after UA style has been
applied. Renamed to 'initial' in the cases where we really mean initial
style to avoid confusion.

Made initial style construction singletons by making the methods in
LayoutStyle and SVGLayoutStyle private. There were a couple of places
where extra copies were created unnecessarily.

R=leviw@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=191795

[rune, 2015-03-12 13:07:00]

rune@opera.com changed reviewers:
+ leviw@chromium.org
- dsinclair@chromium.org

[leviw_travelin_and_unemployed, 2015-03-12 20:12:43]

The CQ bit was checked by leviw@chromium.org

[leviw_travelin_and_unemployed, 2015-03-12 20:12:44]

Great! LGTM.

[commit-bot: I haz the power, 2015-03-12 20:13:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1001833002/1

[commit-bot: I haz the power, 2015-03-12 20:16:27]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=191795