Avoid clearing most RenderObjet bits in styleWillChange

The RenderObject bits touched are always overriden in
updateFromStyle so clearing them was just extra work
and was hurting us on 2 fronts:
- We lose the value of the bits which forced us to rely on
some static variables to store the value until styleDidChange.
- It was very easy to shoot yourself in the foot as querying
either of these booleans would return the cleared value
between styleDidChange and updateFromStyle.

Review URL: https://codereview.chromium.org/87443002

git-svn-id: svn://svn.chromium.org/blink/trunk@162716 bbb929c8-8fbe-4397-9dbb-9b2b20218538