Re-land "[css3-text] Implement text-decoration property shorthand"

Last time I reverted this patch, I forgot to test it in debug mode
*with the runtime feature disabled*. This caused a series of crashes
(see https://code.google.com/p/chromium/issues/detail?id=271234 for
details) and is now fixed - CSSPropertyTextDecoration was already
removed by filterEnabledCSSPropertiesIntoVector() when runtime feature
is disabled - my apologies for not checking it last time.

I spent more time testing this patch and found out a spin-off issue
while copying/pasting HTML code into content editable elements:
https://code.google.com/p/chromium/issues/detail?id=272363

BUG=165462

Review URL: https://chromiumcodereview.appspot.com/23111004

git-svn-id: svn://svn.chromium.org/blink/trunk@156266 bbb929c8-8fbe-4397-9dbb-9b2b20218538