RenderBoxModelObject::firstLetterRemainingText should return a RenderTextFragment*
    
firstLetterRemainingText() returns a RenderObject*, but it is always going to be a RenderTextFragment*.
So, we have to make firstLetterRemainingText return a RenderTextFragment*, which allows to reduce type casting.
    
BUG=none

Review URL: https://codereview.chromium.org/34893002

git-svn-id: svn://svn.chromium.org/blink/trunk@161524 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: add shortcut to resume/step-over buttons on overlay page.

BUG=312741

Review URL: https://codereview.chromium.org/51763010

git-svn-id: svn://svn.chromium.org/blink/trunk@161525 bbb929c8-8fbe-4397-9dbb-9b2b20218538