Oilpan: move editing objects to the heap.

Move the editing commands and style objects to the Oilpan heap, along
with having them use transition types throughout.

R=zerny@chromium.org,haraken@chromium.org,tkent@chromium.org
BUG=357163

Review URL: https://codereview.chromium.org/299353004

git-svn-id: svn://svn.chromium.org/blink/trunk@175079 bbb929c8-8fbe-4397-9dbb-9b2b20218538