collect default, opt-out basic performance timing data in Google Analytics (as custom GA events)

[cvan]

Google Analytics are to be added in issue #169. This issue is for adding performance metrics around page loading, emscripten module loading, and canvas + WebGL performance.

Just like as with issue #169, collecting and submitting this information is opt-out-able and we're including it so we can properly instrument performance issues and improve the stability of this project.

Check out the numerous JavaScript APIs available in the browser with which to instrument various performance data.

---

Parent issue: #165 Related issues:

• 169 for adding default snippet for Mozilla's Google Analytics,

• 167 for creating Help modal,

• 164 for documenting/messaging

[cvan]

found this very relevant list of projects/tools for perf telemetry:

• https://wiki.mozilla.org/CloudServices/DataPipeline
• https://wiki.mozilla.org/CloudServices/DataPipeline/HTTPEdgeServerSpecification
• https://wiki.mozilla.org/CloudServices/DataPipeline/Metadata
• https://github.com/mozilla/telemetry-dashboard/blob/gh-pages/v2/doc.md
• https://anthony-zhang.me/blog/telemetry-demystified/
• https://wiki.mozilla.org/Mobile/Metrics/Redash#Resources
• https://github.com/mozilla/testpilot/blob/master/docs/metrics/telemetry.md
• https://telemetry.mozilla.org/
• https://github.com/mozilla/gecko-dev/blob/master/toolkit/components/telemetry/Histograms.json

"Firefox Telemetry" is not what we're interested in here, but I figured these links are worth looking at (for those who are curious).

[delapuente]

We should assess the feasibility of measuring emscripten module loading (although I think you mean wasm modules) and define what it is to measure canvas + WebGL performance in separated bugs.

[cvan]

basic performance timings handled in PR #189 by @delapuente!

we will file additional specific metrics we want to profile as we discover from users/developers what we need.