dependencies: Add xvfb dependency.

The node package allow use to control xvfb apt package in puppeteer
tests. This help us create a fake display so we can run puppeteer in
headful (headless: false) mode, which is required to use the chrome
extension desktop capture API.

tools/lib/provision.py

@@ -141,6 +141,7 @@ COMMON_DEPENDENCIES = [
     "fonts-freefont-ttf",
     "libappindicator1",
     "xdg-utils",
+    "xvfb",
     # Puppeteer dependencies end here.
 ]