I pulled the trigger to land the previous patch too quickly and missed a
number of comments.

We used to use this mechanism to paint scrollbars, but it's awkward. The
new approach to scrollbars is much cleaner. This mechanism has no other
clients, so we should remove it.

* show build progress; print app sizes

* add todo

* review comments

* remove unused import

This example shows how to build a basic app using a custom Xcode project.
Future patches will bring the functionality up to par with hello_android.

The new mojom.dart code makes mocking services a bit tricky. I've filed
https://github.com/domokit/mojo/issues/786 about improving that.

* run pub get (w/ symlinks) for flutter drive

* review comments

Instead of embedding Flutter.framework and BuildFlutterApp in the Xcode
project, we store these in flutter.git, where we can reference them.

We'll use this functionality to implement some subtle behaviors for tooltips.

* modernize `flutter drive` w.r.t. debug/profil/release options

* make error message prettier

There are still many more left before rendering.dart is complete.

Bump dart SDK to 1.17.0-dev.6.

Remove spurious padding.

Fixes #3980
Fixes #3560

We now explain what coordinate system each argument is expected to be in.

Fixes #4205

* working on making a faster flutter run restart

* clean up todos; fire events on isolate changes

* use the Flutter.FrameworkInitialization event

* review comments

* resolve symlinks in paths to flutter

* review comments

We weren't listening to the decorations to see when they loaded.

Fixes #4185

This reverts commit 8f69cccc.

The new version has an API change. Also, up our SDK requirements to be a
bit more realistic.

* dissallow -release mode on emulators

* have the help text print the default mode

New dev build with more fixes and (fingers-crossed) speed-ups.

Fixes #4186

* fixed issue #4179 bin/flutter fails when linked with relative symlink

* fixed issue #4179 bin/flutter fails when linked with relative symlink

* My second attempt at following symlinks correctly

* compress text assets for docs, when uploading

* reorder args

* ensure old files are deleted

* recurse on the cp

* set source path correctly

This passes the information through Xcode to the `flutter build aot` call via
the environment so that it picks up the right artifacts.

Fixes #4186