Webkit: Using resize handle can select document

[MattMecham]

When you're using Safari/Chrome and resize the editor to make it smaller, the mouse selects the document.

Video: ​http://www.youtube.com/watch?v=l3CPvADGyy8

To reproduce:

Visit creditor.com/demo
Resize to make the editing area larger
Resize to make the editing area smaller but move the mouse pointer above the editor with the mouse button still held down

[Jakub Ś]

DUP of #8518