Changing the rest of the simple CSSValue subclasses to the oilpan transition types.

Only CSSPrimitiveValue and CSSValue remains.
I also had to remove an assignment operator in RawPtr and  make a constructor explicit to avoid ambiguity.
Finally added WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED which expands to nothing when oilpan is enabled and
WTF_MAKE_FAST_ALLOCATED when refcounting is enabled.

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

Review URL: https://codereview.chromium.org/143403009

git-svn-id: svn://svn.chromium.org/blink/trunk@166926 bbb929c8-8fbe-4397-9dbb-9b2b20218538