chore(ci): add Puppeteer-Firefox to CI (#3932)

This patch adds Puppeteer-Firefox bot running on Linux+Node8
on Cirrus CI.

References #3889

.cirrus.yml

@@ -3,7 +3,7 @@ env:
 
 task:
   matrix:
-    - name: node6 (linux)
+    - name: Chromium (node6 + linux)
       container:
         dockerfile: .ci/node6/Dockerfile.linux
       xvfb_start_background_script: Xvfb :99 -ac -screen 0 1024x768x24
@@ -12,7 +12,7 @@ task:
 
 task:
   matrix:
-    - name: node8 (linux)
+    - name: Chromium (node8 + linux)
       container:
         dockerfile: .ci/node8/Dockerfile.linux
       xvfb_start_background_script: Xvfb :99 -ac -screen 0 1024x768x24
@@ -22,10 +22,19 @@ task:
   test_doclint_script: npm run test-doclint
   test_types_script: npm run test-types
 
+task:
+  matrix:
+    - name: Firefox (node8 + linux)
+      container:
+        dockerfile: .ci/node8/Dockerfile.linux
+      xvfb_start_background_script: Xvfb :99 -ac -screen 0 1024x768x24
+  install_script: npm install --unsafe-perm && cd experimental/puppeteer-firefox && npm install --unsafe-perm
+  test_script: npm run funit
+
 task:
   osx_instance:
     image: high-sierra-base
-  name: node8 (macOS)
+  name: Chromium (node8 + macOS)
   env:
     HOMEBREW_NO_AUTO_UPDATE: 1
   node_install_script:

experimental/puppeteer-firefox/lib/Launcher.js

@@ -79,7 +79,12 @@ class Launcher {
           // process group, making it possible to kill child process tree with `.kill(-pid)` command.
           // @see https://nodejs.org/api/child_process.html#child_process_options_detached
           detached: process.platform !== 'win32',
-          stdio
+          stdio,
+          // On linux Juggler ships the libstdc++ it was linked against.
+          env: os.platform() === 'linux' ? {
+            ...process.env,
+            LD_LIBRARY_PATH: `${path.dirname(executablePath)}:${process.env.LD_LIBRARY_PATH}`,
+          } : process.env,
         }
     );
 

experimental/puppeteer-firefox/package.json

@@ -9,7 +9,7 @@
     "node": ">=8.9.4"
   },
   "puppeteer": {
-    "firefox_revision": "d026cf7a14cb7dbe65acc4a4188c570da10a501c"
+    "firefox_revision": "74896383109c18e133bd317b7b2959ae2376f51d"
   },
   "scripts": {
     "install": "node install.js",