[Webkit] Shift enter broken

[Garry Yao]

Reproducing Procedures

1. Open the replace by class example page in FF;
2. Move cursor inside the text, and press 'Shift-Enter';
   • Expected Result: Link break introduced with cursor blinking in front of next paragraph, and If you continue to press this keystroke many times until the the content is outside viewport, latest linebreak will also be scrolled into view;
   • Actual Result: The cursor is still at the end of the first paragraph.

[Garry Yao]

Several fixes in this patch:

1. Fixing a logic error where bogus BR is not guaranteed in webkit when shift enter.
2. The dummy node for hacking scroll into view function should have some content inside;
3. Another defensive logic error within CKDITOR.dom.element::getDocumentPosition.

[Garry Yao]

Adding necessary 'Expected Result' regard auto scrolling into view.