Steps to reproduce:
1. Go to https://demos.telerik.com/kendo-ui/editor/index using IE11
2. Delete a sentence in the editor by repeatedly pressing the backspace key.
The characters are deleted slowly with noticeable lag and jank.
The following profile shows the FPS drop when you repeatedly press backspace.
I believe the call to refreshTools is expensive (for IE) and it is invoked on every keyup for backspace.