* Benchmark for semantic overhead during transitions

* review comments

* [accessibility] Announce index if tab in tab bar

* added TODO

https://github.com/flutter/flutter/issues/10688

* Prefix and Suffix support for TextFields

* Adding Tests

* Removing spurious newline.

* Fixing a small problem with the test

* Review Changes

See https://github.com/flutter/flutter/issues/8986

And add comments explaining why.

Currently this just prints the observatory URL as a JSON event.
Refactored the code to make this fit in.

* resurrect analyzer benchmarks

* move analyzer_benchmark to the more stable linux/android

* report average rather than best result

* Adding first semantics perf test

* review commnts and analyzer fixes

* fix analyzer warning

* Add SemanticsNode.isSelected flag

* Adds example usage to TabBar

See also https://github.com/flutter/engine/pull/3764

* Review comments

* whitespace fixes

* Fix doc ref and update engine roll

* Support 'be' channel so you can download dart-sdk from the tip.

This is triggered when you put 'hash/<build hash>' into dart-sdk.version file. For example, 'hash/c0617d20158955d99d6447036237fe2639ba088c'

* Add README.md

* Fix grammar, spacing, 80 chars, nicer ===

* works using pageview
it’s a bit heavy and scrolls
no documentation or test yet

* docs and tests

* more docs tweak

* revert drive by page view changes

* swap out the indexed stack for a custom thing

* layout everything on the cheap
tests pass

* add more tests

* move back to stack and add docs

* review notes

* build all the tabs once built

* Make dividers one device pixel thick as defined in Material design spec

* Updated divider test to check stroke width

* Clarified dividers with 0 height in the docs

* Updated Divider.height docs according to PR feedback

- How do you handle a tap on text?
- Why is AnimatedOpacity expensive?
- Why would you use a gesture arena team?
...and other minor fixes

We suspect maybe recent failures are caused by race conditions from
running flutter_tools tests in parallel.

Host test runner is flaky. These should be re-enabled once the host
machine has been deflaked.

...and remove some highly specialised methods now that they can just
be implemented directly by the previous callers.

* Add note to .analysis_options about .analysis_options in flutter/plugins

* review comments

Fixes https://github.com/flutter/flutter/issues/10547

* Ensure that SemanticDebugger shows SemanticTree changes from last frame

Fixes https://github.com/flutter/flutter/issues/10566

* Comment for clearification

* Bump to Dart SDK 1.24.0-dev.6.7.

* nits and fixes

* Remove comments unrelated to plugin example app

* Review feedback

This reverts commit c8e4cbf2.