Properly disable nextTick when calling requestAnimationFrame

My previous commit was nonsense because it set the ::performSyncUpdates
flag back to false before the animation frame callback ever got fired.

/cc again @benogle

src/editor-component.coffee

@@ -217,8 +217,9 @@ EditorComponent = React.createClass
   requestAnimationFrame: (fn) ->
     prevPerformSyncUpdates = @performSyncUpdates
     @performSyncUpdates = true
-    requestAnimationFrame(fn)
-    @performSyncUpdates = prevPerformSyncUpdates
+    requestAnimationFrame =>
+      fn()
+      @performSyncUpdates = prevPerformSyncUpdates
 
   getRenderedRowRange: ->
     {editor, lineOverdrawMargin} = @props