Fix selection rect calculation for inline elements with padding

Account for border and padding for inline elements when computing the
height for an inline box. While not needed for layout it is critical for
computing the selection rect.

Change InlineFlowBox::placeBoxesInBlockDirection to accurately account
for the border and padding logical height when computing the selection
height just as the logical top border and padding is taken into account
for the logical top.

Unfortunately this requires a new field in RootInlineBox as the line
bottom and selection bottom can be different.

R=leviw@chromium.org
BUG=385540
TEST=fast/text/selection-with-inline-padding.html

Review URL: https://codereview.chromium.org/331303004

git-svn-id: svn://svn.chromium.org/blink/trunk@176566 bbb929c8-8fbe-4397-9dbb-9b2b20218538