[Oilpan]: Move CSSPropertySourceData, InspectorStyleProperty, CSSStyleSourceData, and CSSRuleSourceData to the oilpan heap using transition types.

Also removed unsused emptyCSSPropertySourceData (adding apavlov as reviewer to verify).

R=ager@chromium.org, erik.corry@gmail.com, haraken@chromium.org, oilpan-reviews@chromium.org, tkent@chromium.org, vegorov@chromium.org, zerny@chromium.org
BUG=341815

Review URL: https://codereview.chromium.org/216553004

git-svn-id: svn://svn.chromium.org/blink/trunk@170550 bbb929c8-8fbe-4397-9dbb-9b2b20218538