…Android manifest (take 2)" (#182522)

### Overview
Re-lands #181632 which TLDR does
the following:

**Same old same old changes from original PR**
- Refactors all engine flags recognized by the Flutter Android embedding
(specifically those previously recognized by
[`FlutterShellArgs`](https://github.com/flutter/flutter/blob/4f5478cce38d837e14b7a032a12500d3fc0f1310/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/FlutterShellArgs.java)
and all of those used to initialize the engine in `FlutterLoader`) into
a new class `FlutterEngineFlags` (`FlutterShellArgs` is kept for now to
maintain backwards compatibility; see
#182153 for details)
- Adds the ability to set engine flags (that are recognized by
`FlutterEngineFlags`) via the manifest
- Adds warnings for developers that set engine flags via `Intent`s as
this will be disabled as part of
#180686.
- Disallows debug/test only flags in release mode

**New changes/fixes**

> [!NOTE]
> This re-land was required because when previously submitted, it caused
b/483299339. I have confirmed that this bug has been fixed in this PR;
see go/flutter-android-setting-flags-in-manifest-perf-comparison for A/B
test results with the previous version of this PR
(#181632) and commit
d6d4a07
of this PR.

- [Critical change] To fix the bug caught by b/483299339,
`--merged-platform-ui-thread` flag is added to `FlutterEngineFlag`s
- [Behavior change, not critical] To avoid more bugs like b/483299339,
`FlutterLoader` allows unrecognized flags specified by the command line
or `Intent` extras to be used to initialize the engine for now (same
behavior as before my original change but I plan to secure this in the
future; see #182557)
- [Small refactor] To speed up manifest argument processing time,
`FlutterLoader` loops through all recognized `FlutterEngineFlag`s to
check if they are present in an application's manifest versus looping
through all metadata in an application's manifest and looking for
recognized `FlutterEngineFlag`s (small improvement for apps with large
manifests)
- [Small refactor] To speed up command line argument processing time,
`FlutterLoader` processes the `--aot-shared-library-name` flag in the
same loop as the other flags, reducing the number of loops
`ensureInitializationComplete` has to do (minimal improvement perf-wise
but kept it in because it's more readable to me)

### Full description
(Mostly copied from #181632)

> [!NOTE]  
> This PR is based on conversation & feedback on
go/flutter-android-harden-engine-shell-arguments.

Adds a mechanism for setting Android engine flags via the manifest. If a
flag is specified on the command line and in manifest metadata, the
value specified on the command line will take precedence. Documentation
is added on this mechanism

Additionally, this PR removes the exposure of`--cache-sksl` command line
flag as per
[https://github.com/flutter/flutter/issues/140310#issuecomment-2708459007](https://www.google.com/url?q=https://github.com/flutter/flutter/issues/140310%23issuecomment-2708459007&sa=D&source=docs&ust=1761156167162464&usg=AOvVaw3a8ubXTtv3apknY2-P9dKe).

Additionally, this PR adds documentation for the only two supported ways
of setting engine flags moving forward -- via the command line or
manifest. The `Intent` mechanism will be removed when
#180686 is completed (intended
to be a follow up to this PR).

As the unit tests in this PR only cover setting flags via manifest in
debug mode, I will follow up this PR with an integration test to test
that flags are appropriately respected/ignored in release mode. See
#178383 for my currently working
but WIP draft.

Part of #172553.

# Follow up work:

- [ ] **Migrate flags all un-migrated flags `FlutterEngineFlags`**
#182852
- [ ] **Add integration test for this new added mechanism.** This will
land as an immediate follow-up to this PR. WIP in
#182241.
- [ ] **Remove support for setting shell arguments via `Intent`.** This
task will be a follow up to this work + the integration test landing,
and will complete work for
#172553. See
#180686 for details.
- [ ] **Only allow known engine flags to be passed to the engine.** This
is more of a P2 but would be a nice additional security feature; see
#182557.

## 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.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [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.
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

**Note**: The Flutter team is currently trialing the use of [Gemini Code
Assist for
GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code).
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disagree with the feedback, please feel free to wait for a Flutter team
member's review for guidance on which automated comments should be
addressed.

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---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

…Android manifest (take 2)" (flutter#182522)

### Overview
Re-lands flutter#181632 which TLDR does
the following:

**Same old same old changes from original PR**
- Refactors all engine flags recognized by the Flutter Android embedding
(specifically those previously recognized by
[`FlutterShellArgs`](https://github.com/flutter/flutter/blob/4f5478cce38d837e14b7a032a12500d3fc0f1310/engine/src/flutter/shell/platform/android/io/flutter/embedding/engine/FlutterShellArgs.java)
and all of those used to initialize the engine in `FlutterLoader`) into
a new class `FlutterEngineFlags` (`FlutterShellArgs` is kept for now to
maintain backwards compatibility; see
flutter#182153 for details)
- Adds the ability to set engine flags (that are recognized by
`FlutterEngineFlags`) via the manifest
- Adds warnings for developers that set engine flags via `Intent`s as
this will be disabled as part of
flutter#180686.
- Disallows debug/test only flags in release mode

**New changes/fixes**

> [!NOTE]
> This re-land was required because when previously submitted, it caused
b/483299339. I have confirmed that this bug has been fixed in this PR;
see go/flutter-android-setting-flags-in-manifest-perf-comparison for A/B
test results with the previous version of this PR
(flutter#181632) and commit
flutter@d6d4a07
of this PR.

- [Critical change] To fix the bug caught by b/483299339,
`--merged-platform-ui-thread` flag is added to `FlutterEngineFlag`s
- [Behavior change, not critical] To avoid more bugs like b/483299339,
`FlutterLoader` allows unrecognized flags specified by the command line
or `Intent` extras to be used to initialize the engine for now (same
behavior as before my original change but I plan to secure this in the
future; see flutter#182557)
- [Small refactor] To speed up manifest argument processing time,
`FlutterLoader` loops through all recognized `FlutterEngineFlag`s to
check if they are present in an application's manifest versus looping
through all metadata in an application's manifest and looking for
recognized `FlutterEngineFlag`s (small improvement for apps with large
manifests)
- [Small refactor] To speed up command line argument processing time,
`FlutterLoader` processes the `--aot-shared-library-name` flag in the
same loop as the other flags, reducing the number of loops
`ensureInitializationComplete` has to do (minimal improvement perf-wise
but kept it in because it's more readable to me)

### Full description
(Mostly copied from flutter#181632)

> [!NOTE]  
> This PR is based on conversation & feedback on
go/flutter-android-harden-engine-shell-arguments.

Adds a mechanism for setting Android engine flags via the manifest. If a
flag is specified on the command line and in manifest metadata, the
value specified on the command line will take precedence. Documentation
is added on this mechanism

Additionally, this PR removes the exposure of`--cache-sksl` command line
flag as per
[https://github.com/flutter/flutter/issues/140310#issuecomment-2708459007](https://www.google.com/url?q=https://github.com/flutter/flutter/issues/140310%23issuecomment-2708459007&sa=D&source=docs&ust=1761156167162464&usg=AOvVaw3a8ubXTtv3apknY2-P9dKe).

Additionally, this PR adds documentation for the only two supported ways
of setting engine flags moving forward -- via the command line or
manifest. The `Intent` mechanism will be removed when
flutter#180686 is completed (intended
to be a follow up to this PR).

As the unit tests in this PR only cover setting flags via manifest in
debug mode, I will follow up this PR with an integration test to test
that flags are appropriately respected/ignored in release mode. See
flutter#178383 for my currently working
but WIP draft.

Part of flutter#172553.

# Follow up work:

- [ ] **Migrate flags all un-migrated flags `FlutterEngineFlags`**
flutter#182852
- [ ] **Add integration test for this new added mechanism.** This will
land as an immediate follow-up to this PR. WIP in
flutter#182241.
- [ ] **Remove support for setting shell arguments via `Intent`.** This
task will be a follow up to this work + the integration test landing,
and will complete work for
flutter#172553. See
flutter#180686 for details.
- [ ] **Only allow known engine flags to be passed to the engine.** This
is more of a P2 but would be a nice additional security feature; see
flutter#182557.

## 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.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [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.
- [x] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

**Note**: The Flutter team is currently trialing the use of [Gemini Code
Assist for
GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code).
Comments from the `gemini-code-assist` bot should not be taken as
authoritative feedback from the Flutter team. If you find its comments
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disagree with the feedback, please feel free to wait for a Flutter team
member's review for guidance on which automated comments should be
addressed.

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---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

…est (flutter#182241)

Adds integration tests for setting engine flags via the manifest for
Flutter Android apps: flutter#182522.
Technically, a continuation of
flutter#178383.

Additionally:

1. Wires up `--test-flag` added in
flutter#182522 so I can test command
line flag specification taking precedence over manifest flag
specification in debug mode only.
2. Fixes documentation/test bug of my previous claim that developers do
not need to specify a manifest metadata value for keys/flags that do not
take arguments in the format of `--flag=value` or
`--flag=value1,value2,...`. This is false; metadata requires a key-value
or key-resource pair (see [documentation
proof](https://developer.android.com/guide/topics/manifest/meta-data-element#:~:text=receiver%3E%0A%3Cservice%3E-,description%3A,-A%20name%2Dvalue)).
3. Refactors devicelab util method for adding metadata to the app
manifest to a central location.

## 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.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [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.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

**Note**: The Flutter team is currently trialing the use of [Gemini Code
Assist for
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Comments from the `gemini-code-assist` bot should not be taken as
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---------

Co-authored-by: jesswrd <[email protected]>

… the manifest (flutter/flutter#182241)

… the manifest (flutter/flutter#182241)

… the manifest (flutter/flutter#182241)

… the manifest (flutter/flutter#182241)

Roll Flutter from c1b14e92dcfb to 31f1802cb859 (46 revisions)

flutter/flutter@c1b14e9...31f1802

2026-04-16 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Run all flutter/flutter macOS tests using Xcode 26 and iOS 26 simulator (#185083)" (flutter/flutter#185145)
2026-04-16 [email protected] Add oval drawing support to the SDF uber shader (flutter/flutter#184903)
2026-04-16 [email protected] Run all flutter/flutter macOS tests using Xcode 26 and iOS 26 simulator (flutter/flutter#185083)
2026-04-16 [email protected] Roll Skia from 2c49b3f9c3c2 to 391cdbe3ffe9 (2 revisions) (flutter/flutter#185138)
2026-04-16 [email protected] Roll Dart SDK from 4ee990654146 to fbddcbe0cd96 (1 revision) (flutter/flutter#185137)
2026-04-16 [email protected] Roll Skia from f4e3cd2c2159 to 2c49b3f9c3c2 (14 revisions) (flutter/flutter#185131)
2026-04-16 [email protected] Roll Dart SDK from 87b7c87e7207 to 4ee990654146 (5 revisions) (flutter/flutter#185108)
2026-04-15 [email protected] Use the `flutteractionsbot` token to push the release branch. (flutter/flutter#184833)
2026-04-15 [email protected] Allow period characters in iOS and macOS framework names (flutter/flutter#184335)
2026-04-15 [email protected] Fix SliverResizingHeader semantic focus (flutter/flutter#179690)
2026-04-15 [email protected] ignore avoid_type_to_string lint rule in flutter_tools (flutter/flutter#184766)
2026-04-15 [email protected] Roll Skia from bda7232e6772 to f4e3cd2c2159 (4 revisions) (flutter/flutter#185063)
2026-04-15 [email protected] Add initial AI guidance for issues (flutter/flutter#184885)
2026-04-15 [email protected] Roll Fuchsia Linux SDK from rB8LAuZL_DwHMssTU... to IdBT8fSMYrYSip65j... (flutter/flutter#185064)
2026-04-15 [email protected] Fix an ordering dependency in the services/system_chrome_test.dart test suite (flutter/flutter#185086)
2026-04-15 98614782+auto-submit[bot]@users.noreply.github.com Reverts "[ios][platform_view]Reland hitTest approach (with a few 2026 update) (#183484)" (flutter/flutter#185082)
2026-04-15 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Run all flutter/flutter macOS tests using Xcode 26 and iOS 26 simulator (#179810)" (flutter/flutter#185067)
2026-04-15 [email protected] Agent rule: Dart editing (flutter/flutter#185045)
2026-04-15 [email protected] [ios][platform_view]Reland hitTest approach (with a few 2026 update) (flutter/flutter#183484)
2026-04-15 [email protected] Run all flutter/flutter macOS tests using Xcode 26 and iOS 26 simulator (flutter/flutter#179810)
2026-04-15 [email protected] Roll Dart SDK from ee5afcef0596 to 87b7c87e7207 (4 revisions) (flutter/flutter#185060)
2026-04-15 [email protected] Roll Skia from 4c382df6a25a to bda7232e6772 (7 revisions) (flutter/flutter#185057)
2026-04-15 [email protected] Remove material import from toggleable_test.dart + draggable_test.dart + obscured_animated_image_test.dart + sliver_constraints_test.dart (flutter/flutter#181774)
2026-04-15 [email protected] refactor: Remove material imports from Widget tests  (flutter/flutter#184877)
2026-04-14 [email protected] Adds missing `await`s on forgotten cases (flutter/flutter#183466)
2026-04-14 [email protected] Use an if-element in a collection literal instead of a conditional expression (flutter/flutter#184830)
2026-04-14 [email protected] update popular issues documentation (flutter/flutter#183196)
2026-04-14 [email protected] [Android] Add integration test for setting engine flags via the manifest (flutter/flutter#182241)
2026-04-14 [email protected] [fuchsia] Ask for both ambient-replace and VMEX to allow for a softer transition. (flutter/flutter#185042)
2026-04-14 [email protected] Make `multiple_windows` follow repo analyzer rules (flutter/flutter#184753)
2026-04-14 [email protected] Ignore incoming deprecated_web_configuration lint (flutter/flutter#184130)
2026-04-14 [email protected] [AGP 9] Update AGP Error (flutter/flutter#185043)
2026-04-14 [email protected] Move widget_preview_scaffold into pub workspace (flutter/flutter#182627)
2026-04-14 [email protected] Fix gles interactive tests (flutter/flutter#181389)
2026-04-14 [email protected] Update customer tests.version (flutter/flutter#185044)
2026-04-14 [email protected] [SKILL] upgrade-browser (flutter/flutter#184894)
2026-04-14 [email protected] [ci] Split up integration.shard dart_data_asset_test.dart (flutter/flutter#185021)
2026-04-14 [email protected] Hold startup lock until after `pub get` to prevent races (flutter/flutter#184294)
2026-04-14 6226493[email protected] Add `--include-example` flag to `flutter clean` for package example projects (flutter/flutter#183455)
2026-04-14 [email protected] Disable multi-pack-index when calling flutter from Xcode (flutter/flutter#184998)
2026-04-14 [email protected] Fix icon tree shaking when building for desktop (flutter/flutter#184249)
2026-04-14 [email protected] Fix killing wrong xcrun command (flutter/flutter#184831)
2026-04-14 [email protected] Allow Xcode build configuration to not contain flavor name (flutter/flutter#183398)
2026-04-14 [email protected] [web] Async rendering for benchmarks (flutter/flutter#184677)
2026-04-14 [email protected] [ci] Split up integration.shard native_assets_test.dart (flutter/flutter#185020)
2026-04-14 [email protected] Skip flutter widget-preview test that times out frequently (flutter/flutter#184988)
...

…5685)

Removed 'bringup' property from android_engine_flags_* tests added in
flutter#182241 because they are not
flaking.

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