perf(android): Move start-reason binder off main thread (JAVA-616)

[runningcode]

📜 Description

On API 35+, AppStartMetrics.registerLifecycleCallbacks performed an ActivityManager.getHistoricalProcessStartReasons(1) binder call synchronously on the main thread. Under auto-init this runs at ContentProvider time (SentryPerformanceProvider.onAppLaunched), blocking the main thread on a system_server round-trip during the coldest part of app start.

This moves the lookup onto a short-lived background daemon thread. The Sentry executor doesn't exist this early (ContentProvider time), so a plain thread is used. cachedStartInfo is now volatile and consumed best-effort:

• Cold/warm classification moves into onActivityCreated: it prefers the resolved ApplicationStartInfo and falls back to the existing pre-API-35 heuristic if the lookup hasn't resolved yet.
• The headless-start path consults the resolved start info before defaulting to COLD.
• getAppStartReason() returns null if the lookup hasn't resolved by the time it is read.

No public API change (apiDump clean).

💡 Motivation and Context

JAVA-616. Fixes #5702.

The binder call stalled the main thread at the most latency-sensitive moment of startup. Measured on a Pixel 10 (API 36) across cold starts, the synchronous call cost ~0.5–2.2 ms of main-thread time (median ~0.7 ms, mean ~0.9 ms). Deferring it reclaims that time from the main thread.

💚 How did you test it?

• AppStartMetricsTestApi35 unit tests updated to inject a synchronous executor and drive onActivityCreated; all pass.
• On-device (Pixel 10, API 36, cold starts via force-stop → launch): before ≈ 0.5–2.2 ms on the main thread (median ~0.7 ms); after, the same work runs on the background thread and cachedStartInfo was ready before the first activity in every observed cold start — even with the sample's artificial start-padding removed — so cold/warm and app.start.reason are preserved in practice.

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

• Consider a follow-up to reuse a shared background executor once one is available that early, instead of a one-off thread.

[linear-code]

JAVA-616

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.50.0 (1)	release

⚙️ sentry-android Build Distribution Settings

[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	320.28 ms	373.06 ms	52.78 ms
Size	0 B	0 B	0 B

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
6b019b7	319.84 ms	333.15 ms	13.31 ms
c3ee041	310.64 ms	361.90 ms	51.26 ms
d501a7e	348.06 ms	431.42 ms	83.36 ms
3998a95	415.94 ms	478.54 ms	62.60 ms
ed33deb	343.30 ms	362.41 ms	19.10 ms
5b1a06b	310.56 ms	362.79 ms	52.22 ms
91bb874	310.68 ms	359.24 ms	48.56 ms
0ee65e9	317.37 ms	366.50 ms	49.13 ms
6edfca2	305.52 ms	432.78 ms	127.26 ms
5e269de	292.83 ms	379.12 ms	86.29 ms

App size

Revision	Plain	With Sentry	Diff
6b019b7	0 B	0 B	0 B
c3ee041	0 B	0 B	0 B
d501a7e	0 B	0 B	0 B
3998a95	1.58 MiB	2.10 MiB	532.96 KiB
ed33deb	1.58 MiB	2.13 MiB	559.52 KiB
5b1a06b	0 B	0 B	0 B
91bb874	1.58 MiB	2.13 MiB	559.07 KiB
0ee65e9	0 B	0 B	0 B
6edfca2	1.58 MiB	2.13 MiB	559.07 KiB
5e269de	0 B	0 B	0 B