Upgrading Chromium Workflow

This document is meant to serve as an overview of what steps are needed on each Chromium upgrade in Electron.

Update libchromiumcontent (a.k.a. libcc)

Clone the repo:

git clone git@github.com:electron/libchromiumcontent.git
cd libchromiumcontent

Run bootstrap script to init and sync git submodules:

./script/bootstrap -v

Update VERSION file to correspond to Chromium version.
Run script/update, it will probably fail applying patches.
Fix failing patches. script/patch.py might help.
- Don't forget to fix patches in the patches-mas/ folder.
Build libcc:

./script/build

Create dist folders which will be used by electron:

./script/create-dist --no_zip
cd dist/main
../../tools/generate_filenames_gypi filenames.gypi src shared_library static_library
cd -

Open a pull request to electron/libchromiumcontent with the changes.
Fix compilation on the all supported platforms/arches.

Update Electron

Set vendor/libchromiumcontent revision to a version with the new Chromium.
- It will be great if GH builds for this libcc version are already green and its archives are already available. Otherwise everyone would need to build libcc locally in order to try build a new Electron.
Set CLANG_REVISION in script/update-clang.sh to match the version Chromium is using. You can find it in file src/tools/clang/scripts/update.py in updated electron/libchromiumcontent repo.
Run script/bootstrap.py.
Upgrade Node.js if you are willing to. See the notes below.
Fix compilation.
Open a pull request on electron/electron with the changes.
- This should include upgrading the submodules in vendor/ as needed.
Fix failing tests.

Upgrade Node.js

Upgrade vendor/node to the Node release that corresponds to the v8 version being used in the new Chromium release. See the v8 versions in Node on https://nodejs.org/en/download/releases for more details.
- You can find v8 version Chromium is using on OmahaProxy. If it's not available check v8/include/v8-version.h in the Chromium checkout.

Troubleshooting

TODO

Verify ffmpeg Support

Electron ships with a version of ffmpeg that includes proprietary codecs by default. A version without these codecs is built and distributed with each release as well. Each Chrome upgrade should verify that switching this version is still supported.

You can verify Electron's support for multiple ffmpeg builds by loading the following page. It should work with the default ffmpeg library distributed with Electron and not work with the ffmpeg library built without proprietary codecs.

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Proprietary Codec Check</title>
  </head>
  <body>
    <p>Checking if Electron is using proprietary codecs by loading video from http://www.quirksmode.org/html5/videos/big_buck_bunny.mp4</p>
    <p id="outcome"></p>
    <video style="display:none" src="http://www.quirksmode.org/html5/videos/big_buck_bunny.mp4" autoplay></video>
    <script>
      const video = document.querySelector('video')
      video.addEventListener('error', ({target}) => {
        if (target.error.code === target.error.MEDIA_ERR_SRC_NOT_SUPPORTED) {
          document.querySelector('#outcome').textContent = 'Not using proprietary codecs, video emitted source not supported error event.'
        } else {
          document.querySelector('#outcome').textContent = `Unexpected error: ${target.error.code}`
        }
      })
      video.addEventListener('playing', () => {
        document.querySelector('#outcome').textContent = 'Using proprietary codecs, video started playing.'
      })
    </script>
  </body>
</html>

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