https://findit-for-me.appspot.com/waterfall/flake?key=ag9zfmZpbmRpdC1mb3ItbWVy_AELEhdNYXN0ZXJGbGFrZUFuYWx5c2lzUm9vdCLFAWNocm9taXVtLm1hYy9NYWMxMC4xMiBUZXN0cy8xNDYxMC93ZWJraXRfbGF5b3V0X3Rlc3RzIG9uIEludGVsIEdQVSBvbiBNYWMgb24gTWFjLTEwLjEyLjYvZG1seWRIVmhiQzkxYzJWeUxXRmpkR2wyWVhScGIyNHRkakl2Wm1GemRDOWxkbVZ1ZEhNdmJXbGtaR3hsUTJ4cFkydEJkWFJ2YzJOeWIyeHNMV05zYVdOckxXaDVjR1Z5YkdsdWF5NW9kRzFzDAsSE01hc3RlckZsYWtlQW5hbHlzaXMYAQw

In this analysis, the swarming task was unable to run the tests at all:

63 files remaining...
Additional test environment:
    CHROME_DEVEL_SANDBOX=/opt/chromium/chrome_sandbox
    CHROME_HEADLESS=1
    LANG=en_US.UTF-8
Command: /usr/bin/python ../../testing/scripts/run_isolated_script_test.py --xvfb ../../third_party/blink/tools/run_web_tests.py --seed 4 --no-show-results --zero-tests-executed-ok --clobber-old-results --exit-after-n-failures 5000 --exit-after-n-crashes-or-timeouts 100 --debug-rwt-logging --results-directory /b/s/w/ioIk5gmZ/layout-test-results --isolated-script-test-output=/b/s/w/ioIk5gmZ/output.json --isolated-script-test-perf-output=/b/s/w/ioIk5gmZ/perftest-output.json --gtest_filter=virtual/user-activation-v2/fast/events/middleClickAutoscroll-click-hyperlink.html --gtest_repeat=30 --test-launcher-retry-limit=0 --gtest_also_run_disabled_tests

Additional test environment:
    CHROME_DEVEL_SANDBOX=/opt/chromium/chrome_sandbox
    CHROME_HEADLESS=1
    LANG=en_US.UTF-8
Command: /usr/bin/python ../../third_party/blink/tools/run_web_tests.py --seed 4 --no-show-results --zero-tests-executed-ok --clobber-old-results --exit-after-n-failures 5000 --exit-after-n-crashes-or-timeouts 100 --debug-rwt-logging --results-directory /b/s/w/ioIk5gmZ/layout-test-results --gtest_filter=virtual/user-activation-v2/fast/events/middleClickAutoscroll-click-hyperlink.html --gtest_repeat=30 --test-launcher-retry-limit=0 --gtest_also_run_disabled_tests --write-full-results-to /b/s/w/ioIk5gmZ/output.json

15:17:25.513 2525 Using port 'mac-mac10.12'
15:17:25.513 2525 Test configuration: <mac10.12, x86, release>
15:17:25.513 2525 View the test results at file:///b/s/w/ioIk5gmZ/layout-test-results/results.html
15:17:25.513 2525 Using random order with seed: 4
15:17:25.513 2525 Baseline search path: mac-mac10.12 -> mac -> generic
15:17:25.513 2525 Using Release build
15:17:25.513 2525 Pixel tests enabled
15:17:25.513 2525 Regular timeout: 6000, slow test timeout: 30000
15:17:25.513 2525 Command line: /b/s/w/ir/out/Release/Content Shell.app/Contents/MacOS/Content Shell --run-web-tests --ignore-certificate-errors-spki-list=Nxvaj3+bY3oVrTc+Jp7m3E3sB1n3lXtnMDCyBsqEXiY=,55qC1nKu2A88ESbFmk5sTPQS/ScG+8DD7P+2bgFA9iM= --user-data-dir -
15:17:25.513 2525 
15:17:25.513 2525 Collecting tests ...
15:17:25.513 2525 Collecting tests ...
15:17:25.583 2525 Manifest not found at /b/s/w/ir/third_party/WebKit/LayoutTests/external/wpt/MANIFEST.json. See  http://crbug.com/698294 
15:17:25.584 2525 Parsing expectations ...
15:17:26.111 2525 Found 1 test; running 1 (30 times each: --repeat-each=30 --iterations=1), skipping 0.
15:17:26.111 2525 Checking build ...
15:17:26.111 2525 Unable to find test driver
15:17:26.112 2525     at /b/s/w/ir/out/Release/Content Shell.app/Contents/MacOS/Content Shell
15:17:26.112 2525 For complete Mac build requirements, please see:
15:17:26.112 2525 
15:17:26.112 2525     https://chromium.googlesource.com/chromium/src/+/master/docs/mac_build_instructions.md
15:17:26.112 2525 Build check failed
15:17:26.112 2525 
15:17:26.112 2525 Testing completed. Exit status: 255

The resulting 0% pass rate is actually undefined, as there are 0 iterations as well.

Not sure if this was caused by the change being a DEPS roll or if there's much that can be done with this analysis, but logging as FYI