…on (#182317)

Fixes #182314

This cherry picks in 2 changes to stable
- #180886
  - The pub roller was busted, and the stable release missed the update
- #180658
  - Preceded manual pub roll, required to pass analysis with above change.

This is a manual cherry pick, following https://github.com/flutter/flutter/blob/main/docs/releases/Flutter-Cherrypick-Process.md

Around about when we created the release, the pub roller was busted. It is fixed now (#180503).

Impacted Users: significant
Impact Description: users cannot upgrade to the latest version
Workaround: None
Risk: Not sure, but the pub roll this is cherry picking landed very very close to the stable release being cut. Analysis and flutter doctor all pass.
Test Coverage: For the widget scaffold change, tests are just relocated
Validation steps: dart-lang/test#2570 (comment)

**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 useful you can update your code accordingly, but if you are unsure or 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.

…e start of "flutter test" output to be optional. (#182335)

This pull request is created by [automatic cherry pick workflow](https://github.com/flutter/flutter/blob/main/docs/releases/Flutter-Cherrypick-Process.md#automatically-creates-a-cherry-pick-request)
Please fill in the form below, and a flutter domain expert will evaluate this cherry pick request.

### Issue Link:
What is the link to the issue this cherry-pick is addressing?

#180903. This is blocking a stable hotfix right now. See https://ci.chromium.org/ui/p/flutter/builders/prod/Linux_mokey%20flutter_test_performance/8971/overview.

### Impact Description:

Maybe impacts some people parsing test output besides us.

### Changelog Description:

Version 1.29 of the Dart test package adds a blank line to test output causing unexpected test failures.

### Workaround:
No need for a workaround/

### Risk:
What is the risk level of this cherry-pick?

### Test Coverage:
Are you confident that your fix is well-tested by automated tests?

### Validation Steps:
What are the steps to validate that this fix works?

< Replace with validation steps here >

)

This pull request is created by [automatic cherry pick workflow](https://github.com/flutter/flutter/blob/main/docs/releases/Flutter-Cherrypick-Process.md#automatically-creates-a-cherry-pick-request)
Please fill in the form below, and a flutter domain expert will evaluate this cherry pick request.

### Issue Link:
What is the link to the issue this cherry-pick is addressing?

#182076

### Impact Description:
What is the impact (ex. visual jank on Samsung phones, app crash, cannot ship an iOS app)?
Does it impact development (ex. flutter doctor crashes when Android Studio is installed),
or the shipping of production apps (the app crashes on launch).
This information is for domain experts and release engineers to understand the consequences of saying yes or no to the cherry pick.

The `--web-define` feature works during development (i.e. `flutter run`), but doesn't work for production (i.e. `flutter build web`).

### Changelog Description:
Explain this cherry pick:
* In one line that is accessible to most Flutter developers.
* That describes the state prior to the fix.
* That includes which platforms are impacted.
See [best practices](https://github.com/flutter/flutter/blob/main/docs/releases/Hotfix-Documentation-Best-Practices.md) for examples.

Fix `flutter build web` ignoring `--web-define` flag

### Workaround:
Is there a workaround for this issue?

No workaround.

### Risk:
What is the risk level of this cherry-pick?

### Test Coverage:
Are you confident that your fix is well-tested by automated tests?

### Validation Steps:
What are the steps to validate that this fix works?

Follow repro steps in #182076

…ot turned on (#182320)

This pull request is created by [automatic cherry pick workflow](https://github.com/flutter/flutter/blob/main/docs/releases/Flutter-Cherrypick-Process.md#automatically-creates-a-cherry-pick-request)

### Issue Link:
What is the link to the issue this cherry-pick is addressing?

#179673

### Impact Description:
What is the impact (ex. visual jank on Samsung phones, app crash, cannot ship an iOS app)?
- Content Sizing is affecting platform views even when content sizing is not enabled via the feature flag.
Does it impact development (ex. flutter doctor crashes when Android Studio is installed),
or the shipping of production apps (the app crashes on launch).
- Shipping of production apps
This information is for domain experts and release engineers to understand the consequences of saying yes or no to the cherry pick.

There is a race condition in the content sizing code that sometimes causes a platform view to not appropriately rotate (as can be seen from the flakey test goldens).  

### Changelog Description:
Explain this cherry pick:
* In one line that is accessible to most Flutter developers.
- Ensures no side effects from content sizing when content sizing is not enabled by the user.
* That describes the state prior to the fix.
- Sometimes platform views will not render as desired.
* That includes which platforms are impacted.
Android

< Replace with changelog description here >
[flutter/179673] When content sizing is not enabled on Android, a race condition can sometimes make platform views not render correctly.

### Workaround:
Is there a workaround for this issue?

No workaround.

### Risk:
What is the risk level of this cherry-pick?

### Test Coverage:
Are you confident that your fix is well-tested by automated tests?

### Validation Steps:
What are the steps to validate that this fix works?

Run the flakey test several times to make sure it passes all the time (as can be seen from the flake being fixed here: https://flutter-dashboard.appspot.com/#/build?taskFilter=Linux_android_emu+android_engine_opengles_tests)

bumping engine version to 87054f6

**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 useful you can update your code accordingly, but if you are unsure or 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.

**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 useful you can update your code accordingly, but if you are unsure or 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.

…ve "position: absolute" (#182299)

This CP pull request was created manually.

Cherry-pick of #181053

### Issue Link:
What is the link to the issue this cherry-pick is addressing?

Closes #182292

### Changelog Description:

Fix bug in multisurfacerenderer where canvases do not have "position: absolute"

### Impact Description:

Platform views not visible on Safari and Firefox.

### Risk:
What is the risk level of this cherry-pick?

### Test Coverage:
Are you confident that your fix is well-tested by automated tests?

### Validation Steps:
What are the steps to validate that this fix works?

Follow repro steps in #182292

…182549)

This pull request is created by [automatic cherry pick workflow](https://github.com/flutter/flutter/blob/main/docs/releases/Flutter-Cherrypick-Process.md#automatically-creates-a-cherry-pick-request)
Please fill in the form below, and a flutter domain expert will evaluate this cherry pick request.

### Issue Link:
What is the link to the issue this cherry-pick is addressing?

#182243

### Impact Description:
What is the impact (ex. visual jank on Samsung phones, app crash, cannot ship an iOS app)?
Does it impact development (ex. flutter doctor crashes when Android Studio is installed),
or the shipping of production apps (the app crashes on launch).
This information is for domain experts and release engineers to understand the consequences of saying yes or no to the cherry pick.

`flutter build web` is broken for apps that use the `{{...}}` pattern in `web/index.html`.

### Changelog Description:
Explain this cherry pick:
* In one line that is accessible to most Flutter developers.
* That describes the state prior to the fix.
* That includes which platforms are impacted.
See [best practices](https://github.com/flutter/flutter/blob/main/docs/releases/Hotfix-Documentation-Best-Practices.md) for examples.

Don't throw an exception if no web define variable is set.

### Workaround:
Is there a workaround for this issue?

It's possible to workaround this issue by adding `--web-define=foo={{foo}}`.

### Risk:
What is the risk level of this cherry-pick?

### Test Coverage:
Are you confident that your fix is well-tested by automated tests?

### Validation Steps:
What are the steps to validate that this fix works?

Follow repro steps in #182243

**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 useful you can update your code accordingly, but if you are unsure or 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.

**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 useful you can update your code accordingly, but if you are unsure or 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.