Simplify RenderFlexibleBox::computeMainAxisExtentForChild
Simplify RenderFlexibleBox::computeMainAxisExtentForChild

We only need to check size.isIntrinsic(), not all of
height/min-height/max-height. We can also use layoutIfNeeded().

No new tests - no behavior change.

R=ojan@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/15112004

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@150355 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs