This reverts commit 215e1b89.

It broke the Mac build: https://build.chromium.org/p/client.flutter/builders/Mac/builds/1097

There are many more places we can use this annotation. This patch starts out
small to test the waters.

This patch starts using the mustCallSuper annotation for several of the key
lifecycle callbacks in the framework. I haven't added it to didUpdateConfig
because there are a large number of non-compliant overrides. We should discuss
whether we want to use it there.

As requested by the material design team.

Fixes #4182

Currently this service just returns mock data, but it exercises the plumbing.

Update analyzer dep to 0.27.4-alpha.9

Update analyzer dep to 0.27.4-alpha.9 to enjoy analyzer perf improvements (https://codereview.chromium.org/2011183004/) (and keep in sync with the SDK).

(This is a revisit to https://github.com/flutter/flutter/pull/4253.)

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