CPU spikes caused by saving PDF to Desktop

[Jesse]

### Affected version

- Ubuntu 19.10
- GNOME 3.34.1
- X11

### Bug summary
Downloading a large (60MB) PDF to the desktop causes CPU spikes at regular intervals. Was not able to reproduce when saving it elsewhere (such as `~/Documents`)

### Steps to reproduce

[PDF](https://openstax.org/details/books/psychology?Book%20details)

This is the PDF I downloaded that presented the issue (it's a free textbook published by OpenStax).

1. Click "Download PDF"
2. Save to the Desktop
3. Verify degraded system performance (see notes below)
4. Delete PDF
5. Verify system performance is no longer degraded

### Relevant logs, screenshots, screencasts etc.

The culprit appears to be `createThumbnail.js`. It appears to be stuck in an infinite loop of starting and stopping a new process. This makes it a bit difficult to monitor. The method that worked for me was to run `top -o %CPU`, press `d`, and set the delay to something short like `0.1`. You should see `createThumbnail` continuously flash on and off the top of the list.

I tested saving and deleting the PDF repeatedly and there were a couple times when it wouldn't cause the issue.

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: gnome-shell-extension-desktop-icons 19.10.2-1
ProcVersionSignature: Ubuntu 5.3.0-40.32-generic 5.3.18
Uname: Linux 5.3.0-40-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu8.5
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Mon Mar 16 03:02:52 2020
InstallationDate: Installed on 2020-03-04 (11 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: gnome-shell-extension-desktop-icons
UpgradeStatus: No upgrade log present (probably fresh install)

[Jesse (roux-jesse)]

Original issue: https://gitlab.gnome.org/GNOME/gnome-shell/issues/2407

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Roger James (rogerjames99)]

If you are experiencing this bug. Try the following.

if the directory "/usr/share/gnome-shell/extensions/desktop-icons@csoriano" rename it to something else. Then restart the desktop (logout then login).

Please report the results of this test back here.

I am trying to correlate information on the part this extension is playing in various desktop rendering glitches.

[Daniel van Vugt (vanvugt)]

Instead of the above, try just running the 'Extensions' app and disabling 'Desktop Icons'.