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.
If the Skia patch is already in Gerrit and there are no associated Chromium changes, then it is possible to just run the Chromium trybots. This will apply the Skia patch and run the bot.
If the Skia patch is already in Gerrit and there are associated Chromium changes, then in the Chromium CL add the following to <chromium>/src/DEPS in the ‘hooks’ array.
{
'name': 'fetch_custom_patch',
'pattern': '.',
'action': [ 'git', '-C', 'src/third_party/skia/',
'fetch', 'https://skia.googlesource.com/skia', 'refs/changes/13/10513/13',
],
},
{
'name': 'apply_custom_patch',
'pattern': '.',
'action': ['git', '-C', 'src/third_party/skia/',
'-c', 'user.name=Custom Patch', '-c', 'user.email=custompatch@example.com',
'cherry-pick', 'FETCH_HEAD',
],
},
Modify the ‘refs/changes/XX/YYYY/ZZ’ to the appropriate values (where YYYY is the numeric change number, ZZ is the patch set number and XX is the last two digits of the numeric change number). This can be seen in the ‘Download’ link on Gerrit.
If this is for a project other than Skia, update the checkout directory and fetch source. Note that this can be used multiple times to apply multiple issues.
An example of this being used can be seen at https://crrev.com/2786433004/#ps1 .
To test locally, run gclient runhooks to update the Skia source code. Note that if your local skia patch in third_party/skia isn‘t clean (e.g., you already applied some patch to it), then gclient runhooks won’t successfully run. In that case, run git reset --hard inside third_party/skia before gclient runhooks.
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': ['python2',
'-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 .
After committing a <chromium>/src/DEPS or <chromium>/src/patch/ change 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.