* 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

Rename State.config to State.widget
Rename State.didUpdateConfig to State.didUpdateWidget
Renamed all State subclasses' local variables named config to something else

After this patch, there are three major text input widgets:

 * EditableText. This widget is a low-level editing control that
   interacts with the IME and displays a blinking cursor.

 * TextField. This widget is a Material Design text field, with all the
   bells and whistles. It is highly configurable and can be reduced down
   to a fairly simple control by setting its `decoration` property to
   null.

 * TextFormField. This widget is a FormField that wraps a TextField.

This patch also replaces the InputValue data model for these widgets
with a Listenable TextEditingController, which is much more flexible.

Fixes #7031

This TODO was fixed by the transition to `Finder` objects.

Rename all the "2" classes related to scrolling to remove the "2". Now that the
old scrolling code is gone, we don't need to use the suffix.

All the clients have migrated to Scrollable2.

For measuring the Dart thread, we care about thread duration (tdur) rather than
wall duration (dur) because we don't want to count the time when the Dart
thread is descheduled (e.g., in preference to the raster thread).

Prior to this change, these benchmarks were mostly measuring whether the OS
decided to finish the Dart thread's time slice or hand over the CPU to the
raster thread to complete the visual part of the frame. Now we actually measure
the work done on the Dart thread.

Also, switch Stepper over to using sliver-based scrolling.

* Small Flutter strong mode cleanup fixes.

These are cases where strong mode down cast composite errors
generally indicated cases that would performance or correctness
issues if Flutter code was run in a strong mode VM.

* Fix Command API so that it is always in terms of Map<String,String>.

* Fix typedef

The finder will only match the widget's ValueKey if both have identical
runtime types

This remove a very brittle aspect of flutter drive, whereby it would
assume a known port instead of explicitly finding out what it was.

Fixes #7692 and hopefully fixes the devicelab tests.

I see these errors in Atom on my Mac. I'm not sure why they're not being
picked up by the bots.

This is handy for debugging a test. Communication is logged to:
* `flutter_driver_commands_{x}.log`, where {x} is an integer, and
* (if requested by user) to stdout

fixes #7473

With frameSync enabled, flutter_driver actions will only be performed
when there are no pending frames in the app under test. This helps with
reducing flakiness.

fixes #7433

It is now handled at a higher level for all commands.

Returns a dump of the application's render tree.

Declares a top-level getter that returns the outputs directory to which
Flutter Driver tests can write any output files. Timeline data defaults
to this directory.