* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

Integrate Strut: Add StrutStyle, expose Strut API, wire up strut with dart:ui, Roll engine 31a7f4d..e7eb1c8 (7 commits) (#26332)

Includes a breaking change to dart:ui ParagraphStyle where lineHeight is renamed to height for consistency with TextStyle.

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

The main purpose of this PR is to make it so that when you set the
initial route and it's a hierarchical route (e.g. `/a/b/c`), it
implies multiple pushes, one for each step of the route (so in that
case, `/`, `/a`, `/a/b`, and `/a/b/c`, in that order). If any of those
routes don't exist, it falls back to '/'.

As part of doing that, I:

 * Changed the default for MaterialApp.initialRoute to honor the
   actual initial route.

 * Added a MaterialApp.onUnknownRoute for handling bad routes.

 * Added a feature to flutter_driver that allows the host test script
   and the device test app to communicate.

 * Added a test to make sure `flutter drive --route` works.
   (Hopefully that will also prove `flutter run --route` works, though
   this isn't testing the `flutter` tool's side of that. My main
   concern is over whether the engine side works.)

 * Fixed `flutter drive` to output the right target file name.

 * Changed how the stocks app represents its data, so that we can
   show a page for a stock before we know if it exists.

 * Made it possible to show a stock page that doesn't exist. It shows
   a progress indicator if we're loading the data, or else shows a
   message saying it doesn't exist.

 * Changed the pathing structure of routes in stocks to work more
   sanely.

 * Made search in the stocks app actually work (before it only worked
   if we happened to accidentally trigger a rebuild). Added a test.

 * Replaced some custom code in the stocks app with a BackButton.

 * Added a "color" feature to BackButton to support the stocks use case.

 * Spaced out the ErrorWidget text a bit more.

 * Added `RouteSettings.copyWith`, which I ended up not using.

 * Improved the error messages around routing.

While I was in some files I made a few formatting fixes, fixed some
code health issues, and also removed `flaky: true` from some devicelab
tests that have been stable for a while. Also added some documentation
here and there.

* Manually fix every use of Point.x and Point.y

Some of these were moved to dx/dy, but not all.

* Manually convert uses of the old gradient API

* Remove old reference to Point.

* Mechanical changes

I applied the following at the root of the Flutter repository:

git ls-files -z | xargs -0 sed -i 's/\bPoint[.]origin\b/Offset.zero/g'
git ls-files -z | xargs -0 sed -i 's/\bPoint[.]lerp\b/Offset.lerp/g'
git ls-files -z | xargs -0 sed -i 's/\bnew Point\b/new Offset/g'
git ls-files -z | xargs -0 sed -i 's/\bconst Point\b/const Offset/g'
git ls-files -z | xargs -0 sed -i 's/\bstatic Point /static Offset /g'
git ls-files -z | xargs -0 sed -i 's/\bfinal Point /final Offset /g'
git ls-files -z | xargs -0 sed -i 's/^\( *\)Point /\1Offset /g'
git ls-files -z | xargs -0 sed -i 's/ui[.]Point\b/ui.Offset/g'
git ls-files -z | xargs -0 sed -i 's/(Point\b/(Offset/g'
git ls-files -z | xargs -0 sed -i 's/\([[{,]\) Point\b/\1 Offset/g'
git ls-files -z | xargs -0 sed -i 's/@required Point\b/@required Offset/g'
git ls-files -z | xargs -0 sed -i 's/<Point>/<Offset>/g'
git ls-files -z | xargs -0 sed -i 's/[.]toOffset()//g'
git ls-files -z | xargs -0 sed -i 's/[.]toPoint()//g'
git ls-files -z | xargs -0 sed -i 's/\bshow Point, /show /g'
git ls-files -z | xargs -0 sed -i 's/\bshow Point;/show Offset;/g'

* Mechanical changes - dartdocs

I applied the following at the root of the Flutter repository:

git ls-files -z | xargs -0 sed -i 's/\ba \[Point\]/an [Offset]/g'
git ls-files -z | xargs -0 sed -i 's/\[Point\]/[Offset]/g'

* Further improvements and a test

* Fix minor errors from rebasing...

* Roll engine

This yak shave went as follows:

Fix https://github.com/flutter/flutter/issues/8795 by adding stocks to
the examples README.

Notice the layers entry in that README isn't quite right either.
Update that.

Check the layers/README file is worth pointing at.

Update the layers/README.

Let's run some of the layer tests to see if they still work.

Oops, need to update them to gradle.

Ok let's try running them again.

Oops, sector is broken.

Add a test for sector.

Fix sector. Find you need to add an assert to a const constructor.

Notice we need to turn const asserts on for the analyzer.

Notice the analysis_options files are out of sync with each other and
with the full list of lints.

Turn on the lints that should be on.

Fix the bugs that finds.

Covers lib/ in package:flutter.

* Print the error message multiple times to avoid overlap with status bar and add paragraph to mock_canvas

Also, make sure that the parent is notified when they change.

Fixes #2298

Turns out there were more clients of the old paragraph API than I expected.
This patch migrates them to the new API.

We'll eventually remove Paragraph#paint.

Fixes #2694

Now a RenderBox is considered hit if one of its children are hit or it itself
decides that it's hit. In particular, empty space inside a flex won't be hit
because none of the children are located there and a RenderFlex doesn't
consider itself hittable.

Fixes #53
Fixes #1221

Now that you import a top-level file for each layer of the Flutter
framework, within the framework we can use relative paths without being
worried about the copy/pasta problem we used to have.

Almost done adding dartdoc to the rendering layer.

If the build stack got long before, it would get cropped.