skia2/site/dev/chrome/multi_repo_trybots.md

Multiple repo Chromium trybots

When a proposed Skia change will require a change in Chromium or Blink it is often helpful to locally create the Chromium and Blink changes and test with the proposed Skia change. This often happens with Skia API changes and changes which affect Blink layout tests. While simple to do locally, this explains how to do so on the Chromium trybots.

The basic idea is to make your Chromium and Blink change in the usual way, but then pull in other changes by modifying the <chromium>/src/DEPS file.

Rietveld

If the the patch to be applied is to a project already in Chromium (like Skia) and the patch is already in Rietveld, then add the following to <chromium>/src/DEPS in the 'hooks' array just before the 'gyp' hook.

  {
    'name': 'apply_custom_patch',
    'pattern': '.',
    'action': ['apply_issue',
               '--root_dir', 'src/third_party/skia',
               '--issue', '1873923002',
               '--patchset', '160001',
               '--server', 'https://codereview.chromium.org',
               '--force',
               '--ignore_deps',
               '-v',
               '-v',
               '--no-auth',
               '--blacklist', 'DEPS'
    ],
  },

An example of this being used can be seen at https://crrev.com/1877673002/#ps120001 .

External changes not in rietveld

If the patch is to files where the above is not possible, then it is still possible to patch the files manually by adding the following to <chromium>/src/DEPS in the 'hooks' array just before the 'gyp' hook.

  {
    'name': 'apply_custom_patch',
    'pattern': '.',
    'action': ['python',
               '-c', 'from distutils.dir_util import copy_tree; copy_tree("src/patch/", "src/");'
    ],
  },

Then, copy all 'out of tree' files into <chromium>/src/patch/, using the same directory structure used by Chromium. When 'gclient runhooks' is run, the files in <chromium>/src/patch/ will be copied to and overwrite corresponding files in <chromium>/src/. For example, if changing <skia>/include/core/SkPath.h, place a copy of the modified SkPath.h at <chromium>/src/patch/third_party/skia/include/core/SkPath.h.

An example of this being used can be seen at https://crrev.com/1866773002/#ps20001 .

Try the patch

After committing these <chromium>/src/DEPS and <chromium>/src/patch/ changes locally, 'git cl upload' can be used in the usual way. Be sure to add 'COMMIT=false' to the issue description to avoid accidentally checking it in.