Improve README.chromium for WPTServe.

third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/README.chromium

 W3C Web Platform Tests in Blink Layout Tests
 
 Design Doc: https://goo.gl/iXUaZd
 
 This directory contains checked out and reduced code from web-platform-tests
 (https://github.com/w3c/web-platform-tests/) required to run WPT tests as part
 of Blink's test infrastructure and some maintenance/configuration code.
 
 The third party code lives entirely in the wpt subdirectory:
 Tools/Scripts/webkitpy/thirdparty/wpt/wpt
@@ skipping 33 matching lines @@
 
 WPTWhiteList
 ============
 The explicit list of files being kept, everything else not on this list is
 deleted when running "./checkout.sh reduce". Use this file to control what gets
 checked in and try to keep the list as small as possible (use what you need).
 
 certs/
 ======
 This directory contains a private key and a certificate of WPTServe, and files
-for self-signed CA. WPTServe generates them on the fly with "openssl" command in
-the default setting, but we check in pre-generated files to avoid "openssl"
+for self-signed CA. By default, WPTServe generates these files using the
+"openssl" command, but we check in pre-generated files to avoid "openssl"
 dependency.
 
 These certificates will expire in January 2025. Here is an instruction to
 re-generate them:
 
 1. Add "openssl" command to PATH.
 2. Apply the following change locally:
 
 diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/wpt.config.json b/third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/wpt.config.json
 index 6243954..84fd3f4 100644
@@ skipping 26 matching lines @@
          """SSL environment that creates a local CA and host certificate using OpenSSL.
  
          By default this will look in base_path for existing certificates that are still
 
 3. Run third_party/WebKit/Tools/Scripts/run-blink-wptserve
 4. Type Enter key to terminate it.
 5. Revert the local change.  e.g. git reset --hard HEAD
 6. Replace certs/ with wpt/_certs/
    % rm -fr certs
    % mv wpt/_certs certs
-7. Look at *.pem, and update "January 2025" in this document to new expiration
-   date.
+7. Look at *.pem, and update "January 2025" in this document and expiration_date
+   in wptserve.py to new expiration date.
 8. git commit -a
 9. git cl upload, etc.
 
+TODO(tkent): Make a script to re-generate keys and certificates.
+
 **
 
 Rolling in WPT
 
 When rolling in new versions of WPT support, use WPTHeads to adjust the HEAD
 positions. You can then call "./checkout.sh clone" which will pull in all the
 code and required submodules.
 
 You can check in the latest code by setting the HEAD commit-ish to "master" on
 each line, afterwards make sure to use the actual SHA1s to lock down the HEAD
@@ skipping 12 matching lines @@
 **
 
 Configuration
 
 Read instructions in WPT README:
 https://github.com/w3c/web-platform-tests/blob/master/README.md
 
 Also, check out the WPTServe Documentation
 (https://wptserve.readthedocs.org/en/latest/).
 
-For setting up SSL, refer to Tools/Scripts/webkitpy/thirdparty/wpt/wpt/_certs
-(which gets generated on the first run).
-
 Note that editing /etc/hosts is not required for run-webkit-tests since
 content_shell is invoked with flags to map all *.test domains to 127.0.0.1.
 
 **
 
 Running web-platform-tests with enabled WPTServe on a local machine
 
 Starting run-webkit-tests with the --enable-wptserve flag will start WPTServe
 for tests which live in LayoutTests/imported/wpt.
 
 WPTServe starts HTTP/S and WS/S servers as separate processes.
 
 The content_shell used to run the tests will receive the URL of each test
 (instead of a filename). The document root http://web-platform.test/ maps to
 LayoutTests/imported/wpt. HTTPS tests are enabled by default.
 
 Example run:
 
 ./Tools/Scripts/run-webkit-tests \
     --debug \
     --enable-wptserve \
     --no-new-test-results \
     imported/wpt