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Time Travel Debugging WPT on Windows

I've had trouble getting Time Travel Debugging (TTD) working with debugging WPT from my chromium repo on Windows. Having finally gotten it working, I wanted to document the steps I took to get it working:

  1. Follow the install TTD instructions. This will install the Microsoft.TimeTravelDebugging app package and will expose the ttd.exe command line executable.

  2. Disable hardware enforced stack protection. See Kernel-mode Hardware-enforced Stack Protection of where to find the option, but disable it. TTD cannot trace an executable with this enabled.

  3. Add a WPT virtual test suite to pass in --no-sandbox. TTD doesn't work when Chromium sandboxing is on for a process. Edit third_party/blink/web_tests/VirtualTestSuites and add a new entry like the following:

  {
    "prefix": "no-sandbox",
    "platforms": [
      "Linux",
      "Mac",
      "Win"
    ],
    "bases": [ "" ],
    "args": [
      "--no-sandbox"
    ],
    "owners": [
      "example@example.com"
    ],
    "expires": "Jul 17, 2026"
  },
  1. Run TTD to monitor the WPT headless_shell.exe processes. In an admin prompt run the following, but modify the -out path to wherever you want the TTD trace files to be created. Pick a path that can store files of several GBs in size. Leave this running.
Admin> ttd.exe -out C:\users\davris\tmp -monitor headless_shell.exe -noUI
  1. Run your WPT tests using the virtual test suite, with timeouts extended, and using a release build in a non-admin prompt. Note in the following command the test starts with the test suite prefix virtual/no-sandbox/ and the --timeout-multiplier is set to 5 to allow for the much slower execution when TTD tracing.
Non-Admin> Q:\cr\src\third_party\blink\tools\run_wpt_tests -t Q:\cr\src\out\release_x64 virtual/no-sandbox/external/wpt/service-workers/service-worker/service-worker-header.https.html --no-retry-failures --verbose --driver-logging --timeout-multiplier 5
  1. Once the WPT finishes you should find a bunch of *.run files in the output directory you specified in step 4. These are the TTD trace files. You can open them in WinDbg and use !peb to see the command line and which kind of chromium process kind. But usually the .run file of the renderer process you want is the last one and largest one, and for the browser process is the first one.