Consolidates the asset path lookup logic from FlutterDartProject and FlutterMain().

* Lookup FTLAssetsPath when deducing assets path on ios

* WS

* Proper fix

* Another whitespace fix

* Allow embedder clients to provide a resource context. Closes flutter/flutter#14263.

See https://github.com/flutter/flutter/pull/14275 for framework side change.

Also includes some minor clean-ups for consistency. 

Required for https://github.com/flutter/flutter/issues/13469.

Skia is trimming some of these transitive includes

* Update dart version in engine to 8d9d68751a505426eb5f59a9d29f103fde6bd474

* Update third party license files.

* Update license file.

* Update license file.

Fixes https://github.com/flutter/flutter/issues/14093

isRRect returns false for RRects that are oval.

Fixes flutter/flutter#14186

Fixes https://github.com/flutter/flutter/issues/13392.

Fixes https://github.com/flutter/flutter/issues/14082

Fixes https://github.com/flutter/flutter/issues/10284

* Support .packages option in frontend_server, bundle_path in main_mac.

This is needed to be able to run  in  mode.

* Remove byte store tests

* Remove unused import

* Fix formatting

* Enable flutter test argument passing on win and linux.

* Fix formatting

* Fix host_os literal for windows

* Fix slashes

* Roll Dart to 93d8c9fe2a2c22dc95ec85866af108cfab71ad06.

* Fix analyzer nits

* Try to pin dependency for tools/licenses to convert 2.0.1. Add verbose flag to pub get

* Pin dart to dev.16 to overcome pub issue

* Revert "Try to pin dependency for tools/licenses to convert 2.0.1. Add verbose flag to pub get"

This reverts commit d525a83f4494a511996226d328a5208d4651d46e as it is no
longer needed, was added to diagnose the problem, which turned out to be
a problem with pub in latest dart dev release.

* Fix license hash

* Reintroduce api methods and tests

In https://github.com/flutter/engine/pull/4554 I removed the .packages
file in the frontend_server directory, because it was out of sync with
the pubspec.yaml. It seems like the right solution is to run `pub get`
when we get the dependencies, i.e. when we run `gclient sync`.

Being out of sync is a problem because it means that running "pub get"
in that directory changes what packages are being used, and changes
the `.packages` file, which leads to having to revert changes before
committing code, etc. Having to regularly update this file doesn't
make much sense either, since the files that were missing were files
that are obtained from the network (e.g. the `io` package as used by
the `test` package).

Previously, (see
https://github.com/flutter/engine/pull/3982#issuecomment-323213199),
we did not do this because we did not want the build to call into the
network. This still does not call into the network during the _build_
phase, only during `gclient sync` (which is when all the dependencies
are brought down).

Currently the network dependencies only matter for running tests. We
should make sure this remains the case. Ideally we wouldn't even
depend on those.

* Analysis cleanup of the Dart in the Engine repo

* Update painting.dart

* Update painting.dart

Reland 86430be6 with a fix for Windows build

Cuts 30% from hot-reload benchmarks with `--preview-dart-2`

Fixes https://github.com/flutter/flutter/issues/14092

Scenic doesn't currently support arbitrary shaped frames.