[flutter_tools] Report when the browser disconnects during a web test run - #192198

… run (flutter#192198)

Fixes flutter#191920

When the browser closes its connection to the test host during `flutter
test --platform chrome`, unfinished suites are reported as `did not
complete` without a diagnostic explaining the lost connection. The issue
includes a deterministic renderer-kill reproduction confirmed on master.

The WebSocket can close before the browser's process exit notification
arrives. `BrowserManager.close()` sets `_closed`, and `Chromium.close()`
sets `_didClose`, so cleanup can suppress the existing process-exit
diagnostics. A renderer or page disconnect can also leave the browser
process alive until the tool closes it.

This change does two things when the browser disconnects before the
manager initiates shutdown:

- Reports the disconnect before cleanup starts, so the run explains why
its suites did not complete.
- Records the unexpected disconnect and keeps the manager's exit-code
callback active after cleanup starts. Cleanup begins immediately,
without a grace-period timeout. The exit-code message describes an exit
after disconnection, rather than claiming that a cleanup-induced exit
was the original crash.

Intentional shutdown remains silent.

## Tests

Six `BrowserManager` regressions in
`test/commands.shard/hermetic/flutter_web_platform_test.dart` cover
unexpected disconnection, immediate cleanup, exit notifications arriving
after cleanup starts, the process exiting before the connection closes,
intentional shutdown, and normal cleanup without a false crash
diagnostic.

All 43 tests across that file and `test/web.shard/chrome_test.dart`
pass. Formatting, analysis of the changed files, and `git diff --check`
pass.

Also verified with real Chrome using the tool from source: normal
completion, an ordinary assertion failure, a renderer kill, and a
browser-process kill. Neither normal completion nor the assertion
failure produces a false disconnect diagnostic. Both kill paths report
the disconnect and clean up the test browser; the process-kill path
reports exit code -9. Both kill paths reproduce the missing disconnect
diagnostic on unpatched master.

The broader Flutter Tools run attempted 340 test files. It found 16
failures that also reproduce on unpatched master, in widget-preview path
normalization, native-assets filesystem-guard handling, and the
workspace-member tests. A native-assets batch also hung and was stopped.
The full suite is not green; the browser-related tests are.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [AI contribution guidelines] and understand my
responsibilities, or I am not using AI tools.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant in-code documentation (doc comments with
`///`).
- [x] If this PR introduces a new feature or capability, I created and
linked a website documentation issue or PR in [flutter/website] (or
verified none is needed).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [ ] All existing and new tests are passing. Browser-related tests
pass; the broader failures reproduce on unpatched master as noted above.

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---------

Co-authored-by: Ben Konyi <[email protected]>

Roll Flutter from fcfb4f203eae to 934720261be0 (38 revisions)

flutter/flutter@fcfb4f2...9347202

2026-11-03 [email protected] Roll Skia from 5bceaa033999 to c733ad3e37cb (5 revisions) (flutter/flutter#195872)
2026-11-03 [email protected] Roll Skia from 34d2bf479385 to 5bceaa033999 (9 revisions) (flutter/flutter#195864)
2026-11-03 [email protected] fix: prefer pointer events over semantics tap for mouse clicks on web (flutter/flutter#191529)
2026-11-03 [email protected] [VPAT] Expose a semantics text field value while it is not being edited (flutter/flutter#195445)
2026-11-03 [email protected] [Impeller] Make a GL context current before constructing an AiksContext without a surface (flutter/flutter#195629)
2026-11-03 [email protected] [flutter_tools] Eliminate globals.dart from project.dart (flutter/flutter#194066)
2026-11-03 [email protected] [tool] Complete context runner elimination and migrate AppContext usages to ToolContext (flutter/flutter#190797)
2026-11-03 [email protected] [web] Unify font collections between CanvasKit and Skwasm (flutter/flutter#195539)
2026-11-03 [email protected] [Android] Replay predictive back state for retained engines (flutter/flutter#192286)
2026-11-03 [email protected] [vulkan]: Adds depth/stencil synchronization for subpasses (flutter/flutter#195689)
2026-11-03 [email protected] [web] Honor requested upscaling in instantiateImageCodecWithSize and ImageDescriptor.instantiateCodec (flutter/flutter#195836)
2026-11-03 [email protected] Roll Skia from 866b61ca92c9 to 34d2bf479385 (9 revisions) (flutter/flutter#195848)
2026-11-03 [email protected] Roll Fuchsia Test Scripts from xl1LWBuppzu-BnOzV... to B6zarykZp6PKWRueg... (flutter/flutter#195847)
2026-11-03 [email protected] Remove unused ffi (flutter/flutter#195710)
2026-11-02 [email protected] Revert: [Android] Let the raster thread use every core of a chip without little cores (flutter/flutter#195838)
2026-11-02 [email protected] Run 10 impeller iOS benchmarks as one devicelab task (flutter/flutter#195661)
2026-11-02 [email protected] Use named uniforms instead of setFloat in StretchEffect (flutter/flutter#195372)
2026-11-02 [email protected] [flutter_tools] Report when the browser disconnects during a web test run (flutter/flutter#192198)
2026-11-02 [email protected] fix: Resolve memory leak in image_list example (flutter/flutter#189526)
2026-11-02 [email protected] Only run the common local engine configurations in presubmit (flutter/flutter#195688)
2026-11-02 [email protected] Update gcloud_version to version [email protected] (flutter/flutter#195769)
2026-11-02 [email protected] [Impeller] Order the Vulkan copy-texture-to-texture layout transition after the copy (flutter/flutter#195814)
2026-11-02 [email protected] [Impeller] Order the Vulkan ResizeTexture layout transition after its blit (flutter/flutter#195721)
2026-11-02 [email protected] [web] Fix CanvasKit fragment shader uniforms being freed or mutated after recording (flutter/flutter#195718)
2026-11-02 [email protected] Roll Fuchsia Linux SDK from MqypI6RNyVZ_FLUE-... to T_-6-6X1lDMghhAvX... (flutter/flutter#195809)
2026-11-02 [email protected] [Android] Log why Impeller falls back to OpenGLES (flutter/flutter#194764)
2026-11-02 [email protected] Roll Skia from 3f35fb6e591b to 866b61ca92c9 (11 revisions) (flutter/flutter#195802)
2026-11-02 [email protected] Roll Skia from 3f35fb6e591b to 866b61ca92c9 (11 revisions) (flutter/flutter#195802)
2026-11-02 [email protected] Only run the common local engine configurations in presubmit (flutter/flutter#195688)
2026-11-02 [email protected] Balance tool_integration_tests subshards by expected duration (flutter/flutter#195628)
2026-11-02 [email protected] [web_paragraph] Map code units without a cluster to a cluster (flutter/flutter#195384)
2026-11-02 [email protected] [web] Hide synthetic autofill inputs from assistive technology (flutter/flutter#195618)
2026-11-02 [email protected] Roll Packages from 3742a4e to 3f34a6f (8 revisions) (flutter/flutter#195795)
2026-11-02 [email protected] [web] Unskip web tests that pass on CanvasKit and Skwasm: platform_view_test, route_notification_messages_test (flutter/flutter#195605)
2026-11-02 [email protected] Roll Skia from e5ad3868b8db to 3f35fb6e591b (1 revision) (flutter/flutter#195789)
2026-11-02 [email protected] Roll Skia from f5215e74aa16 to e5ad3868b8db (3 revisions) (flutter/flutter#195779)
2026-11-02 [email protected] Roll Skia from e43478a2f9f8 to f5215e74aa16 (1 revision) (flutter/flutter#195776)
2026-11-01 [email protected] Roll Fuchsia Linux SDK from kW0A0xxNkqf38ljm4... to MqypI6RNyVZ_FLUE-... (flutter/flutter#195768)

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