Only notify the flowthread about style changes on actual descendants.

Only notify the flowthread about style changes on actual descendants.

Calling flowThreadContainingBlock() on the flow thread itself returns the flow
thread, but the flow thread obviouly isn't a true descendant of itself, so
let's avoid calling flowThreadDescendantStyleWillChange() and
flowThreadDescendantStyleDidChange() then. There's currently no way any harm
could be done if the flow tread were indeed treated as a descendant of itself
here, but it's just wrong and bad.

R=dsinclair@chromium.org,jchaffraix@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=195863

[dsinclair, 2015-05-25 13:45:15]

The CQ bit was checked by dsinclair@chromium.org

[dsinclair, 2015-05-25 13:45:15]

lgtm

[commit-bot: I haz the power, 2015-05-25 13:45:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1155023002/1

[commit-bot: I haz the power, 2015-05-25 13:47:42]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=195863