Comment 8 for bug 1628866

Chiming in to say I experience the same thing, extreme slowdown and stuttering in chromium but only when a second window is open on a separate workspace.

uname -a: Linux Latitude-7480 4.8.0-41-generic #44-Ubuntu SMP Fri Mar 3 15:27:17 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

glxinfo:

name of display: :0
display: :0 screen: 0
direct rendering: Yes
server glx vendor string: SGI
server glx version string: 1.4
Extended renderer info (GLX_MESA_query_renderer):
    Vendor: Intel Open Source Technology Center (0x8086)
    Device: Mesa DRI Intel(R) Kabylake GT2 (0x5916)
    Version: 12.0.6
    Accelerated: yes
    Video memory: 3072MB
    Unified memory: yes
    Preferred profile: core (0x1)
    Max core profile version: 4.3
    Max compat profile version: 3.0
    Max GLES1 profile version: 1.1
    Max GLES[23] profile version: 3.1
*truncated*, more info available if needed

From the previous posts it seems that the Intel graphics are at fault perhaps?