Added early exit in the LayoutBox::nodeAtPoint.
Added early exit in the LayoutBox::nodeAtPoint.

nodeAtPoint was recursing down through its children even when there was
no possibility that any of its descendents would be hit. This change
avoids traversing the children. This change is correct because the
visual overflow only excludes positioned overflow, which will get hit
tested through the DeprecatedPaintLayer code path.

BUG=

Review URL: https://codereview.chromium.org/1144363005

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@196081 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk