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Fixes #177974

Description

  • Forces WASM single-threading when running a web app as a Chrome extension.
BEFORE AFTER
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@ksokolovskyi ksokolovskyi requested a review from mdebbar December 3, 2025 11:57
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It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing. If you believe this PR qualifies for a test exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!). The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.

@github-actions github-actions bot added engine flutter/engine related. See also e: labels. platform-web Web applications specifically labels Dec 3, 2025
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Code Review

This pull request effectively addresses an issue where multi-threaded WASM fails within Chrome extensions by forcing single-threaded execution in that environment. A new isChromeExtension utility is introduced for reliable detection, and this is integrated into the skwasm_loader logic. The change correctly anticipates scenarios where an extension might have crossOriginIsolated enabled but still be subject to security policies that prevent worker creation. The accompanying TypeScript definition updates and minor corrections to a JSDoc type and a comment typo are also appropriate. The changes are well-targeted and robust.

@ksokolovskyi
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Hi @mdebbar, there is no way to test engine/src/flutter/lib/web_ui/flutter_js code for now. Do you have an idea how I can test the changes in this PR?

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Thanks for fixing this, @ksokolovskyi !

@ksokolovskyi
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@mdebbar @kevmoo thanks a lot for your reviews!
Could you please take a look at the comments in the latest commit when you have time?

@ksokolovskyi ksokolovskyi added the autosubmit Merge PR when tree becomes green via auto submit App label Dec 5, 2025
@auto-submit auto-submit bot added this pull request to the merge queue Dec 5, 2025
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@mdebbar @kevmoo thanks a lot for your reviews!

Merged via the queue into flutter:master with commit 6e9567e Dec 5, 2025
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@flutter-dashboard flutter-dashboard bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Dec 5, 2025
engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Dec 5, 2025
engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Dec 5, 2025
auto-submit bot pushed a commit to flutter/packages that referenced this pull request Dec 5, 2025
Roll Flutter from 69d8710fadcd to 5b8720312a94 (42 revisions)

flutter/flutter@69d8710...5b87203

2025-12-05 [email protected] Roll Packages from d39e481 to b17d3ff (3 revisions) (flutter/flutter#179505)
2025-12-05 [email protected] Move target_cpu into use_rbe block in Fuchsia build (flutter/flutter#179458)
2025-12-05 [email protected] Roll Skia from fe6bf18a3f6b to a31411879251 (3 revisions) (flutter/flutter#179499)
2025-12-05 [email protected] Force WASM single threading in Chrome extensions. (flutter/flutter#179400)
2025-12-05 [email protected] Roll Skia from aea282ea0bcd to fe6bf18a3f6b (7 revisions) (flutter/flutter#179489)
2025-12-05 [email protected] fix: check both pointer count and action before reusing MotionEvent (flutter/flutter#178528)
2025-12-05 [email protected] Roll Fuchsia Linux SDK from VtDPX2k1kosHxjKUE... to vDeTl_KBeLJY8nCAx... (flutter/flutter#179478)
2025-12-05 [email protected] [ Widget Preview ] Add embedded Widget Inspector support (flutter/flutter#178116)
2025-12-05 [email protected] bubble up fragment shader errors (flutter/flutter#179363)
2025-12-05 [email protected] Roll Dart SDK from eda82318e193 to 42fe3327abca (1 revision) (flutter/flutter#179472)
2025-12-05 [email protected] [Android 16] Use AVD With New Android Renderer (flutter/flutter#179306)
2025-12-05 [email protected] Unpin `package:dwds` dependency (flutter/flutter#179462)
2025-12-05 [email protected] [Impeller] include uniform info in impellerc json reflections (flutter/flutter#179317)
2025-12-05 [email protected] Roll Skia from 1591b066f49b to aea282ea0bcd (1 revision) (flutter/flutter#179468)
2025-12-04 [email protected] Roll Skia from e1923478562b to 1591b066f49b (3 revisions) (flutter/flutter#179460)
2025-12-04 [email protected] Cherry-pick flutter 3.38.4 changelog back to master. (flutter/flutter#179463)
2025-12-04 [email protected] [web] Add clone method to LayerPicture and dispose pictures in PictureLayer (flutter/flutter#179162)
2025-12-04 [email protected] Fixes merge conflict from high bitrate texture tests (flutter/flutter#179416)
2025-12-04 [email protected] Fix typos in `VirtualDisplayController.java` (flutter/flutter#179411)
2025-12-04 [email protected] Roll Dart SDK from 2de44cc08970 to eda82318e193 (1 revision) (flutter/flutter#179453)
2025-12-04 [email protected] Roll Skia from 55d94a54f453 to e1923478562b (1 revision) (flutter/flutter#179449)
2025-12-04 [email protected] Roll Packages from 8cb4903 to d39e481 (8 revisions) (flutter/flutter#179451)
2025-12-04 [email protected] Add DropdownMenu.selectOnly (flutter/flutter#179189)
2025-12-04 [email protected] Roll Dart SDK from 7e6bfc6af55c to 2de44cc08970 (6 revisions) (flutter/flutter#179443)
2025-12-04 [email protected] Roll Skia from b8f79d7316c0 to 55d94a54f453 (1 revision) (flutter/flutter#179439)
2025-12-04 [email protected] Revise README for link updates and terminology changes (flutter/flutter#179357)
2025-12-04 [email protected] Roll Skia from ce19122e3982 to b8f79d7316c0 (3 revisions) (flutter/flutter#179436)
2025-12-04 [email protected] Update some BottomNavigationBar comments to reflect theme normalization (flutter/flutter#179404)
2025-12-04 [email protected] Replace use of eglCreateImage with eglCreateImageKHR to reduce EGL requirement (flutter/flutter#179310)
2025-12-04 [email protected] Roll Skia from 81a9a0751f00 to ce19122e3982 (5 revisions) (flutter/flutter#179430)
2025-12-04 [email protected] [impellerc] adds entry prefix flag to avoid shader collisions (flutter/flutter#179160)
2025-12-04 [email protected] [Windows] Allow apps to prefer high power GPUs (flutter/flutter#177653)
2025-12-04 [email protected] [ Infra ] Shard `Windows tool_tests_commands` (flutter/flutter#179409)
2025-12-04 [email protected] [flutter_tools] Fix filename typo (flutter/flutter#179427)
2025-12-04 [email protected] Marks Linux_pixel_7pro draw_arcs_all_stroke_styles_perf__timeline_summary to be unflaky (flutter/flutter#179392)
2025-12-03 [email protected] Marks Mac_ios draw_arcs_all_fill_styles_perf_ios__timeline_summary to be unflaky (flutter/flutter#179391)
2025-12-03 [email protected] Marks Linux_pixel_7pro draw_arcs_all_fill_styles_perf__timeline_summary to be unflaky (flutter/flutter#179390)
2025-12-03 [email protected] Roll Abseil to 564023aa5376 (flutter/flutter#179421)
2025-12-03 [email protected] Made wide gamut tests give more information in their failure (flutter/flutter#179415)
2025-12-03 [email protected] Roll Skia from c20f797ab6f9 to 81a9a0751f00 (5 revisions) (flutter/flutter#179417)
2025-12-03 [email protected] Migrate samples and docs to RadioGroup (flutter/flutter#179158)
2025-12-03 [email protected] Roll Dart SDK to 3.11.0-200.1.beta (flutter/flutter#179399)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-packages
...
reidbaker pushed a commit to AbdeMohlbi/flutter that referenced this pull request Dec 10, 2025
Fixes flutter#177974

### Description
- Forces WASM single-threading when running a web app as a Chrome
extension.

| BEFORE | AFTER |
| - | - |
| <video alt="before"
src="https://github.com/user-attachments/assets/4b67fce6-4bd7-4646-a0db-dc6ad2ec70aa"
/> | <video alt="after"
src="https://github.com/user-attachments/assets/3f0df9c5-7524-40db-a631-776777f855f9"/>
|

## Pre-launch Checklist

- [X] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [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.
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [ ] 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.
- [X] All existing and new tests are passing.

<!-- Links -->
[Contributor Guide]:
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[Tree Hygiene]:
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https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
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[Features we expect every widget to implement]:
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[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
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[Data Driven Fixes]:
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---------

Co-authored-by: Kevin Moore <[email protected]>
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[BUG] Flutter multi-threaded WASM web app cannot run as Chrome Extension

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