Bug 1731594: Update the updatebot dockerfile to prepare for pdf.js r=jewilde

Differential Revision: https://phabricator.services.mozilla.com/D142366

taskcluster/docker/updatebot/privileged-setup.sh

@@ -35,14 +35,27 @@ apt-get install -y --no-install-recommends \
     python3-requests \
     python3-requests-unixsocket \
     python3-setuptools \
+    nodejs \
+    npm \
     openssh-client \
+    rsync \
     wget
 
 mkdir -p /builds/worker/.mozbuild
 chown -R worker:worker /builds/worker/
-
 export GOPATH=/builds/worker/go
 
+# pdf.js setup
+# We want to aviod downloading a ton of packages all the time, so
+# we will preload the pdf.js repo (and packages) in the Docker image
+# and only update it at runtime. This means that the `./mach vendor`
+# behavior for pdf.js will also be kind of custom
+npm install -g gulp-cli
+cd /builds/worker/
+git clone https://github.com/mozilla/pdf.js.git
+cd /builds/worker/pdf.js
+npm ci
+
 # Build Google's Cloud SQL Proxy from source
 cd /builds/worker/
 mkdir cloud_sql_proxy