Fix incorrect style recalculation of text-decoration properties.

This change adds the color and style of each decoration to the
AppliedTextDecoration class. This is needed to make RenderStyle
diffs compute correctly when the color or style of a decoration is changed.

The color-resolving code in RenderObject has been moved to RenderStyle to
enable use from both RenderStyle and RenderObject.

This patch also makes it possible to implement multiple decorations
on the same line. (A future patch).

BUG=350840, 315271
TEST=text-decoration-color-recalc.html
     text-decoration-style-recalc.html
     text-decoration-line-recalc.html

Review URL: https://codereview.chromium.org/280503003

git-svn-id: svn://svn.chromium.org/blink/trunk@174285 bbb929c8-8fbe-4397-9dbb-9b2b20218538