✨ [RUM-10292] Add notRestoredReasons support

[rgaignault]

Motivation

During the recent WebPerformance Working Group, Google Chrome engineers highlighted that nearly all back/forward cache (BFCache) navigations fail due to blockers such as Cache-Control: no-store and active WebSockets. To improve visibility and help developers optimize their pages, Chrome recently introduced the notRestoredReasons API. Surfacing these details in Datadog RUM will allow engineers to understand why their pages are not benefiting from BFCache.

Changes

This PR extends our navigation timings collection to capture notRestoredReasons from the PerformanceNavigationTiming entry.

Test instructions

Checklist

• [x] Tested locally
• [ ] Tested on staging
• [ ] Added unit tests for this change.
• [ ] Added e2e/integration tests for this change.

[datadog-datadog-prod-us1[bot]]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage
• Patch Coverage: 100.00%
• Total Coverage: 92.57% (+0.00%)
View detailed report

_{This comment will be updated automatically if new data arrives.
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[rgaignault]

/to-staging

[dd-devflow-routing-codex[bot]]

View all feedbacks in Devflow UI.

2025-09-03 10:25:30 UTC :information_source: Start processing command /to-staging

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2025-09-03 10:25:37 UTC :information_source: Branch Integration: starting soon, merge expected in approximately 12m (p90)

Commit a86fd07f15 will soon be integrated into staging-36.

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2025-09-03 10:38:28 UTC :information_source: Branch Integration: this commit was successfully integrated

Commit a86fd07f15 has been merged into staging-36 in merge commit 520ad6a620.

Check out the triggered pipeline on Gitlab 🦊

If you need to revert this integration, you can use the following command: /code revert-integration -b staging-36

[cit-pr-commenter[bot]]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	155.93 KiB	156.16 KiB	236 B	0.15%	✅
Rum Recorder	19.53 KiB	19.53 KiB	0 B	0.00%	✅
Rum Profiler	5.18 KiB	5.18 KiB	0 B	0.00%	✅
Logs	55.12 KiB	55.12 KiB	0 B	0.00%	✅
Flagging	N/A	931 B	931 B	N/A%	✅
Rum Slim	113.80 KiB	114.03 KiB	236 B	0.20%	✅
Worker	23.60 KiB	23.60 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base Average Cpu Time (ms)	Local Average Cpu Time (ms)	𝚫
addglobalcontext	0.005	0.008	0.003
addaction	0.015	0.032	0.017
addtiming	0.004	0.005	0.001
adderror	0.015	0.021	0.006
startstopsessionreplayrecording	0.001	0.001	0.000
startview	0.004	0.009	0.004
logmessage	0.019	0.033	0.013

🧠 Memory Performance

Action Name	Base Consumption Memory (bytes)	Local Consumption Memory (bytes)	𝚫 (bytes)
addglobalcontext	24.77 KiB	26.22 KiB	1.45 KiB
addaction	43.47 KiB	47.00 KiB	3.53 KiB
addtiming	25.22 KiB	24.43 KiB	-803 B
adderror	48.54 KiB	50.43 KiB	1.89 KiB
startstopsessionreplayrecording	24.52 KiB	23.73 KiB	-817 B
startview	421.01 KiB	424.04 KiB	3.03 KiB
logmessage	42.04 KiB	44.44 KiB	2.40 KiB

🔗 RealWorld

[thomas-lebeau]

Are we able to see these new data on staging?