Fixes #24750.

Fixes https://github.com/flutter/flutter/issues/21887

What KeepAlive does is different from the Offstage widget. Let's not confuse these two and be more speicific in the wording for KeepAlive.

This modifies our flutter_tools crash reports to include the error
message. This error message may contain personally identifying
information (PII), such as a file system path on the developer's
local machine that may contain user names, project code names,
etc. To disable crash reporting, the developer can run the
following command:

    flutter config --no-analytics

For more information on what gets reported during crashes of the
flutter tool, see:

https://github.com/flutter/flutter/wiki/Flutter-CLI-crash-reporting

In Dart 2, asserts no longer accept non-bool values so this rule is
made redundant by the Dart analyzer's basic checks and is no longer
necessary.

The rule will be removed in a future Linter release.

Fixes https://github.com/flutter/flutter/issues/24413

Followup to https://github.com/flutter/website/pull/1949, as requested by @Hixie in https://github.com/flutter/website/issues/1634.

cc @kwalrath

This fixes https://github.com/flutter/flutter/issues/25092

Fixes #20313.

https://github.com/flutter/engine/compare/72c7a7567228...7375a0f414bd

git log 72c7a7567228..7375a0f414bd --no-merges --oneline
7375a0f41 Roll Skia to 57d29eaf2ed7518983d9e91fd5219f4cfc181f88 (flutter/engine#7024)


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If the roll is causing failures, please contact the current sheriff (liyuqian@google.com), and stop
the roller if necessary.

* build tests - AOT on all, APK on Linux, IPA on Mac

We hypothesize that many first-time users creating a new project will look at the README.md as a starting point for "what next". As we've updated our documentation particularly for new users, having better links to our codelabs and cookbooks will help them be productive.

72c7a7567 Prepend [NSLocale currentLocale] for first locale on iOS to ensure countryCode exists. Allow language-only locales.

Now that dartdoc automatically generates snapshots for external dart tools, I can remove my path hack from the dartdoc_options.yaml file.

This will allow other packages to again build dartdocs (e.g. plugins) that link to Flutter's dartdocs, and allow me to re-enable dartdoc's cross-linking test that was disabled because of this hack.

* 2f706bea0 Fix EXIF orentation problem (flutter/engine#6974)

* be973ea19 Roll Skia to bb37aba39910ef1a95cdcbb5b85d99cdabf3c362 (flutter/engine#6975)

https://github.com/flutter/engine/compare/5bf4deb4353c...2ab019412dce

git log 5bf4deb4353c..2ab019412dce --no-merges --oneline
2ab019412 Use application_kernel_asset in flutter_tester (flutter/engine#6972)


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https://github.com/flutter/engine/compare/84e3b137a16d...5bf4deb4353c

git log 84e3b137a16d..5bf4deb4353c --no-merges --oneline
5bf4deb43 Update Dartdoc for SceneBuilder#addPlatformView (flutter/engine#6957)


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Picks up changes that unblock the Fuchsia roll https://github.com/flutter/engine/pull/6949.

https://github.com/flutter/engine/compare/25d99cd25780...eebc6a589585

git log 25d99cd25780..eebc6a589585 --no-merges --oneline
eebc6a589 Roll Skia to 988f54e4689b3d9fb6d5220e02b418f5cfa2b6db (flutter/engine#6931)


The AutoRoll server is located here: https://autoroll.skia.org/r/flutter-engine-flutter-autoroll

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https://github.com/flutter/engine/compare/99e73d8c64ed...25d99cd25780

git log 99e73d8c64ed..25d99cd25780 --no-merges --oneline
25d99cd25 Use software renderer in embedder unittests (flutter/engine#6928)


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Documentation for the AutoRoller is here:
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If the roll is causing failures, please contact the current sheriff, who should
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https://github.com/flutter/engine/compare/1e37b99ac07d...99e73d8c64ed

git log 1e37b99ac07d..99e73d8c64ed --no-merges --oneline
99e73d8c6 Roll buildroot to 29a5d76757ec12655c0562b317830f669bd44ea7. (flutter/engine#6929)
df2e9393a load default splash screen when not init with engine (flutter/engine#6925)


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