System Information
Operating system: Windows 10
Graphics card: GeForce GTX 1080ti

Blender Version
Broken:
2.80, 74db65e5424, blender2.8, 2018-12-06

Short description of error

When you are in edit mode of Grease Pencil Object, if you try to open Pie Menu with Tab, you have to wait for a bit.
Opening Pie Menu in other modes ( Object, Draw, Sculpt, Weight Paint) works fine.
This issue only occurs when " Tab for Pie Menu " option in user preference is ON.

Exact steps for others to reproduce the error

1. Open user preference, go to Input, turn on Tab for Pie Menu.
2. Add Grease Pencil Object, go to edit mode then press Tab to open Pie Menu. You should notice a lag.