Since upgrade to Gnome Ubuntu 16.10, my mouse is slow and cursor small on gnome shell menus

I upgraded 2 days ago to Gnome Ubuntu 16.10.
Since then, my mouse is 2x slower and my cursor is 2x smaller...:
- during Gnome startup (about 1 or 2 seconds on my system)
- on Gnome Shell menus

The cursor gets back to normal after I open a GTK application (such as Nautilus, but not Google Chrome). But the mouse is still slow anyway.
I have an Asus UX305 with an HiDPI screen (3200x1800).

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: xorg 1:7.7+13ubuntu4
ProcVersionSignature: Ubuntu 4.8.0-22.24-generic 4.8.0
Uname: Linux 4.8.0-22-generic x86_64
ApportVersion: 2.20.3-0ubuntu8
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: None
CurrentDesktop: GNOME
Date: Mon Oct 17 22:05:50 2016
DistUpgraded: 2016-10-15 22:12:07,962 DEBUG icon theme changed, re-reading
DistroCodename: yakkety
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes
GraphicsCard:
 Intel Corporation HD Graphics 520 [8086:1916] (rev 07) (prog-if 00 [VGA controller])
   Subsystem: ASUSTeK Computer Inc. HD Graphics 520 [1043:1000]
InstallationDate: Installed on 2016-09-21 (26 days ago)
InstallationMedia: Ubuntu-GNOME 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160720)
Lsusb:
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 004: ID 8087:0a2a Intel Corp.
 Bus 001 Device 003: ID 04f2:b56b Chicony Electronics Co., Ltd
 Bus 001 Device 002: ID 045e:07b2 Microsoft Corp.
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: ASUSTeK COMPUTER INC. UX305UA
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.8.0-22-generic.efi.signed root=/dev/mapper/ubuntu--gnome--vg-root ro noprompt quiet splash acpi_osi= vt.handoff=7
SourcePackage: xorg
UpgradeStatus: Upgraded to yakkety on 2016-10-15 (1 days ago)
dmi.bios.date: 10/12/2015
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: UX305UA.201
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: UX305UA
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.asset.tag: ATN12345678901234567
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrUX305UA.201:bd10/12/2015:svnASUSTeKCOMPUTERINC.:pnUX305UA:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnUX305UA:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:
dmi.product.name: UX305UA
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.
version.compiz: compiz N/A
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.70-1
version.libgl1-mesa-dri: libgl1-mesa-dri 12.0.3-1ubuntu2
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 12.0.3-1ubuntu2
version.xserver-xorg-core: xserver-xorg-core 2:1.18.4-1ubuntu6
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.2-1ubuntu1
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.7.1-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20160706-1ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-2