Worker: List test file locations in README.md

Workers and worklets interact with various features, and tests are scattered
among Chromium codebase. This sometimes caused us to forget to add test cases,
and notice some features are broken after they are shipped.

To avoid the situation as much as possible, this CL lists locations where we
should add tests in README.md.

Bug: n/a
Change-Id: Ie0dfc875f4a8149e7c820d9491c75aea418a87ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1839277
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703197}

third_party/blink/renderer/core/workers/README.md

@@ -79,6 +79,48 @@ Note that, where off-the-main-thread top-level fetch is NOT enabled
 (e.g. classic workers), the worker scripts are fetched on the main thread and
 thus WorkerOrWorkletGlobalScope and the worker thread are not involved.
 
+# Tests
+
+When you add a new worker or worklet type, please consider adding tests in
+following files and directories to check integration with the underlying worker
+and worklet infrastructure.
+
+- Web Platform Tests
+  - [workers/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/workers/)
+  - [worklets/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/worklets/)
+- Web tests
+  - [webexposed/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/webexposed/)
+  - [workers/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/http/tests/workers/)
+  - [worklet/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/http/tests/worklet/)
+- Unit tests
+  - [content/browser/worker_host/](https://cs.chromium.org/chromium/src/content/browser/worker_host/)
+  - [content/renderer/worker/](https://cs.chromium.org/chromium/src/content/renderer/worker/)
+  - [third_party/blink/renderer/core/workers/](https://cs.chromium.org/chromium/src/third_party/blink/renderer/core/workers/)
+- Browser tests
+  - [chrome/browser/chrome_worker_browsertest.cc](https://cs.chromium.org/chromium/src/chrome/browser/chrome_worker_browsertest.cc)
+  - [content/browser/worker_host/worker_browsertest.cc](https://cs.chromium.org/chromium/src/content/browser/worker_host/worker_browsertest.cc)
+
+Workers and worklets interact with various features. You should also add tests
+in the following files and directories to avoid breakage.
+
+- Web Platform Tests
+  - [content-security-policy/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/content-security-policy/)
+  - [fetch/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/fetch/)
+  - [mixed-content/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/mixed-content/)
+  - [performance-timeline/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/performance-timeline/)
+  - [referrer-policy/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/referrer-policy/)
+  - [resource-timing/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/resource-timing/)
+  - [secure-contexts/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/secure-contexts/)
+  - [service-workers/service-worker/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/service-workers/service-worker/)
+  - [upgrade-insecure-requests/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/upgrade-insecure-requests/)
+  - [websockets/](https://cs.chromium.org/chromium/src/third_party/blink/web_tests/external/wpt/websockets/)
+- Browser tests
+  - [chrome/browser/chrome_do_not_track_browsertest.cc](https://cs.chromium.org/chromium/src/chrome/browser/chrome_do_not_track_browsertest.cc)
+  - [chrome/browser/chrome_worker_browsertest.cc](https://cs.chromium.org/chromium/src/chrome/browser/chrome_worker_browsertest.cc)
+  - [chrome/browser/extensions/api/web_request/web_request_apitest.cc](https://cs.chromium.org/chromium/src/chrome/browser/extensions/api/web_request/web_request_apitest.cc)
+  - [chrome/browser/ssl/ssl_browsertest.cc](https://cs.chromium.org/chromium/src/chrome/browser/ssl/ssl_browsertest.cc)
+  - [chrome/browser/subresource_filter/subresource_filter_browsertest.cc](https://cs.chromium.org/chromium/src/chrome/browser/subresource_filter/subresource_filter_browsertest.cc)
+
 # References
 
 - [WorkerGlobalScope Initialization](https://docs.google.com/document/d/1JCv8TD2nPLNC2iRCp_D1OM4I3uTS0HoEobuTymaMqgw/edit?usp=sharing) (April 1, 2019)