* Semantic hit test order for Slivers

* ++

* fix double space

* refactoring

* fix test

* comment fix

* tests

* remove accidental debugDumpSemanticsTree

* review comments

* fix button

* Introduce a Directionality inherited widget which sets the ambient LTR vs RTL mode (defaulting to null, which means you cannot use directionality-influenced values).

* Make it possible to configure Padding (including Container.padding and Container.margin) using a directionality-agnostic EdgeInsets variant.

* Provide textDirection and verticalDirection controls on Row and Column to make them RTL-aware.

* Introduce a variant of FractionalOffset based on the EdgeInsets variant. Not yet actually used.

* Fix all the tests that depended on Row defaulting to LTR.

This change re-introduces skipping AOT snapshot builds if input sources
and outputs have not changed since the last snapshot build, assuming a
build for the same platform in the same build mode.

This reverts commit 3d5afb5a.
It includes the following changes relative to the original:
  1. Include the entrypoint source in the checksums
  2. include the build mode in the checksums
  3. include the target platform in the checksums

* refactor to ensureAction + some related doc fixes

* Update docs for markNeedsSemanticsUpdate

* rewording

* rewording

* ensureAction test

* ensureAction test

* ensureAction test

* more tests

* refactor to allways reset node

* tiny fixes

* more test

* doc fixes

* one more test

* review comments

Adds excludes for new test added in
13dda7cf (#11557)

This change ensures that snapshot build checksums used to avoid
duplicate builds are invalidated by a change to framework revision
(in case gen_snapshot is updated), as well as by build mode.

Currently, only FLX snapshotting uses checksums to avoid duplicate
builds. FLX snapshotting is always done with BuildMode.debug, so didn't
include build mode in the checksum file.

* Fix paintBounds/semanticsBounds of RenderSliver

* another test

* Properly update semantics when Material/Cupertino Slider are disabled

* whitespace fix

* fix style

`stiffness` is the name of a spring's `k` input on [iOS](https://developer.apple.com/documentation/quartzcore/caspringanimation), [Android](https://developer.android.com/topic/libraries/support-library/preview/spring-animation.html), and the [Web](https://github.com/skevy/wobble/blob/bbc0f831e234f2d24fb905f2ec278c134d69ed68/src/index.js#L11-L22).  To ensure the API is familiar to and easily understood by developers coming from other platforms, Flutter should follow this convention as well.

This is a minimally-breaking change.  Across [all of GitHub](https://github.com/search?l=Dart&q=springConstant&type=Code&utf8=%E2%9C%93), there are only 2 uses of the `springConstant` API (in Mondrian).  Those can be easily changed to use this name.

Closes #11684

* refactor to assembleSemanticNode

* ++

* cleanup

* fix test

* add note

* review comments

* review feedback

* import fix

* another import fix

* refactor to ensure tag

* tests, tests, tests

* analyzer fixes

* review comments

During FLX snapshotting, changes to (or absence of) any of the following
should trigger re-snapshot:

  1. main() entrypoint source
  2. transitive closure of sources reachable from the entrypoint source
  3. the output snapshot

Fixes https://github.com/flutter/flutter/issues/11722

This patch supports basic filtering of log lines from physical iOS
devices, similar to existing functionality for iOS simulator logging.

This patch also suppresses the following two log messages which are
emitted at app startup on iOS 10.3 devices:
  libMobileGestalt MobileGestaltSupport.m:153: pid 123 (Runner) does not have sandbox access for frZQaeyWLUvLjeuEK43hmg and IS NOT appropriately entitled
  libMobileGestalt MobileGestalt.c:550: no access to InverseDeviceID (see <rdar://problem/11744455>)

These properties had a high cost in the documentation because they're
all top-level properties, and there's really very little reason for
these values to be configurable in the first place.

Allows the user to specify the kind of project to create. The default is 'app'. Other choices are 'plugin' (the old '--plugin' behavior), and 'package'.

A Flutter 'package' is a Dart package that depends on Flutter, but does not contain native code.

Fixes #10377.

* Add comments to 3 methods that were missing comments.

Fix out of order (getter, private field, setter) tuple

* Code review fix.

The flakiness of commands_test is generally visible via:

```
drive:stdout:   Expected: 'log: paint'
drive:stdout:     Actual: ''
drive:stdout:      Which: is different. Both strings start the same, but the actual value is missing the following trailing characters: log: paint ...
```

By returning the name of the test we will be able to understand if
another test is running by reading the `Actual` value