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Accessibility Performance Measurements

Accessibility support can have a negative impact on performance, so it is important to test for regressions and to improve performance over time. This can be done with Chromium's performance testing framework, Telemetry.

The metrics for accessibility are defined in third_party/catapult/tracing/tracing/metrics/accessibility_metric.html.

Stories

A story is a url to load and actions to take on that page.

Accessibility stories are defined in tools/perf/page_sets/system_health/accessibility_stories.py. If a particular web page seems slow, you may add a new story here to track its performance.

Running stories from the command line

To run all accessibility stories locally using the currently installed Canary browser:

tools/perf/run_benchmark system_health.common_desktop \
  --story-filter="accessibility.*" \
  --browser canary

To run the same set of tests on your own compiled version of Chrome:

tools/perf/run_benchmark system_health.common_desktop \
  --story-filter="accessibility.*" \
  --browser=exact \
  --browser-executable=out/Release/chrome

For more information, see the Telemetry documentation or command-line help for tools/perf/run_benchmark.

Capture web page replay for new or modified stories

You should capture web page replay information whenever you add or modify a story. The following command captures the web page replay for all accessibility stories:

tools/perf/record_wpr desktop_system_health_story_set \
  --story-filter="accessibility.*" \
  --browser canary

Running this will upload the web page replay data captured and modify tools/perf/page_sets/data/system_health_desktop.json, which should be submitted as part of your changelist. For more information, see Record a page set.

Blink Perf

Blink perf tests are microbenchmarks that track the performance of a small function or operation in isolation. You can find these tests in third_party/blink/perf_tests/accessibility/.

To run these tests locally on your own compiled Chrome:

tools/perf/run_benchmark blink_perf.accessibility \
  --browser=exact \
  --browser-executable=out/Release/chrome

Results

The results can be found at https://chromeperf.appspot.com.

Google-internal Info

More information on analytics and performance, including some additional Google-internal resources, can be found at go/chrome-a11y/resources/analytics-performance.