Merge 181487 "Editing: Let Selection.collapse with null clears s..."

Merge 181487 "Editing: Let Selection.collapse with null clears s..."

> Editing: Let Selection.collapse with null clears selection.
> 
> The current spec says Selection.collapse(null) raises exception and the 
> implementation follows.
> However, many web apps assume that chrome clears selection when 
> Selection.collapse(null) calls.
> Thus we revert the behavior.
> 
> BUG=395318
> 
> Review URL: https://codereview.chromium.org/546703003

TBR=yoichio@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181788

[yoichio, 2014-09-11 04:23:35]

Committed patchset #1 (id:1) manually as r181788.