Make ':after' triangle larger so that the border of div is covered

When zooming in the border of the div is visible over the :after
pseudo element.
 - Update top and bottom triangle mixins to include @extra argument
 - Update pseudo elements to use the new mixin and position them
   correctly according the extra size

Bug: 73550
Change-Id: I05b9c74a675c69e407c4c78771504f447da754c5
article: Fix distance between image and text (landscape image & non flipped)

Change-Id: I4fb6891cd89546b6a55b6952be7e1a6df41fa0b5
Merge "article: Fix distance between image and text (landscape image & non flipped)"
Merge "Make ':after' triangle larger so that the border of div is covered"