Clear baseRenderStyle on detach.

Clear baseRenderStyle on detach.

ActiveAnimations::baseRenderStyle was only nulled correctly from
styleForElement, but that method is not always called when clearing the
styleChangeType(). For instance when the we have detached the element, but
don't need to create a renderer for it when re-attaching.

This bug caused the baseRenderStyle to survive moving an element between
documents triggering the assert checking that the baseRenderStyle was
correct.

Clearing the baseRenderStyle unconditionally on detach() should fix this.

R=dstockwell@chromium.org,esprehn@chromium.org
BUG=427433
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184515

[dstockwell, 2014-10-28 10:37:38]

lgtm

[rune, 2014-10-28 11:54:14]

The CQ bit was checked by rune@opera.com

[commit-bot: I haz the power, 2014-10-28 11:55:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/642773004/1

[commit-bot: I haz the power, 2014-10-28 13:01:30]

Committed patchset #1 (id:1) as 184515