Remove vendor prefix

`window.webkitRequestAnimationFrame` is being deprecated in CEF 1916 and `window.requestAnimationFrame` now works in brackets-shell master, so convert calls.

cc @JeffryBooher 

**Testing:**

**Resizer.js**: drag side panel right edge to change width and verify panel redraws as you drag.

**BezierEditor.js**: Create CSS rule with declaration something like this:

```CSS
    transition-timing-function: cubic-bezier(.62, 0, 1, .98);
```

Drag control points and verify curve redraws as you drag.