Check in documentation for WPT import and export to //docs.

docs/testing/web_platform_tests.md

+# Web Platform Tests
+
+The W3C provides a large number of conformance tests for different aspects of

[foolip, 2017/01/29 10:21:47]

Nit: s/W3C/Web Platform Tests project/

[qyearsley, 2017/01/29 19:44:41]

Done

+the Web Platform. Currently the tests are hosted on GitHub. There are two main
+repositories, one for the CSS Working Group (aka csswg-test), and one for pretty
+much everything else (aka web-platform-tests). There is a plan to merge
+csswg-test into web-platform-tests, so later, there will be only one repository.
+
+[TOC]
+
+## Import
+
+Chromium has mirrors (web-platform-tests, csswg-test) of the GitHub repos, and
+periodically imports a subset of the tests so that they are run as part of the
+regular Blink layout test testing process.
+
+Note that currently the main reason we do not run more of the W3C tests is
+because they are (probably) mostly redundant with Blink's existing tests, and so

[foolip, 2017/01/29 10:21:47]

I don't think this is the reason really. Although it is a concern, are people
holding off importing relevant tests because of this?

Maybe reword this to explain the concern and what has to be done to overcome it?
(A lot of tedious manual work to compare what test are covering.)

[qyearsley, 2017/01/29 19:44:42]

This was just copied over from the earlier sites page, so I think that this is
out of date. I think that this paragraph is necessary; now removed.

+we would double the running time of the layout tests for little benefit. Ideally
+we would identify the tests that are redundant and remove Blink's copies, so
+that we run just the W3C tests where possible.
+
+The end goals for this whole process are to: Be able to run the W3C tests
+unmodified locally just as easily as we can run the Blink tests Ensure that we

[foolip, 2017/01/29 10:21:47]

Missing punctuation, or was this a bullet list?

[qyearsley, 2017/01/29 19:44:41]

This was a numbered list, but I think it can be a paragraph; now changed.

+are tracking tip-of-tree in the W3C repositories as closely as possible Run as
+many of the W3C tests as possible
+
+### Automatic Import Process
+
+There is an automatic [w3c-test-autoroller
+builder](https://build.chromium.org/p/chromium.infra.cron/builders/w3c-test-autoroller)
+for regularly updating our local copies of web-platform-tests.
+
+```bash
+Tools/Scripts/wpt-import --auto-import wpt
+Tools/Scripts/wpt-import --auto-import css
+```
+
+### Importing New W3C Tests
+
+We control which tests are imported via `LayoutTests/W3CImportExpectations`,
+which has a list of directories to skip during import. This means that any new
+tests and directories that show up in the W3C repos are automatically imported.
+
+To pull the latest versions of the tests that are currently being imported
+(i.e., you don't need to change the blacklist), all you have to do is run:

[foolip, 2017/01/29 10:21:47]

Suggest blocklist, or the filename itself.

[qyearsley, 2017/01/29 19:44:41]

Now changed to just have the filename of the script inline with a link to where
it is in the repository; also changed the title of this section.

+
+```bash
+Tools/Scripts/wpt-import wpt
+Tools/Scripts/wpt-import css
+```
+
+That script will pull the latest version of the tests from our mirrors of the
+W3C repos. If any new versions of tests are found, they will be committed
+locally to your local repository. You may then upload the changes.
+
+If you wish to add more tests (by un-skipping some of the directories currently
+skipped in `W3CImportExpectations`), you can modify that file locally and commit
+it, and on the next auto-import, the new tests should be imported. If you want
+to import immediately, you can also run `wpt-import --allow-local-commits`.
+
+## Contributing Blink tests back to the W3C
+
+If you need to make changes to Web Platform Tests, just commit your changes
+directly to our version in `LayoutTests/external/wpt` and the changes will be
+automatically upstreamed within 24 hours.
+
+Note: if you're adding a new test in `external/wpt`, you'll need to re-generate
+MANIFEST.json manually until [CL 2644783003](https://crrev.com/2644783003) is
+landed. The command to do so is:
+
+```bash
+Tools/Scripts/webkitpy/thirdparty/wpt/wpt/manifest --work \
+    --tests-root=LayoutTests/external/wpt
+```
+
+### Where can I find the code for the WPT import and export tools?
+
+-   Exporter:
+    [Tools/Scripts/wpt-export](../../third_party/WebKit/Tools/Scripts/wpt-export)
+-   Importer:
+    [Tools/Scripts/wpt-import](../../third_party/WebKit/Tools/Scripts/wpt-import)
+-   Libraries:
+    [Tools/Scripts/webkitpy/w3c](../../third_party/WebKit/Tools/Scripts/webkitpy/w3c)
+
+### Will the exported commits be linked to my GitHub profile?
+
+The email you commit with (e.g. user@chromium.org) will be the author of the
+commit on GitHub. You can add it as a secondary address on your GitHub account
+to link your exported commits to your GitHub profile. What if there are
+conflicts?

[foolip, 2017/01/29 10:21:47]

A link to GitHub went missing here, and missing section formatting?

[qyearsley, 2017/01/29 19:44:42]

Fixed.

+
+This cannot be avoided entirely as the two repositories are independent, but
+should be rare with frequent imports and exports. When it does happen, manual
+intervention will be needed and in non-trivial cases you may be asked to help
+resolve the conflict.
+
+### Direct pull requests
+
+It's still possible to make direct pull requests to web-platform-tests. The
+processes for getting new tests committed the W3C repos are at
+[http://testthewebforward.org/docs/]. Some specifics are at
+[http://testthewebforward.org/docs/github-101.html].