A change in overflow mode requires calculation of the text size and resetting
the overflow shader

Subsequent operations like debugAssertDoesMeetConstraints() may do layout
operations that alter _textPainter's state.

Fixes https://github.com/flutter/flutter/issues/9372

* 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

* Fix tests to use Ahem, and helpful changes around that

- Fix fonts that had metric-specific behaviours.

- LiveTestWidgetsFlutterBinding.allowAllFrames has been renamed
  to LiveTestWidgetsFlutterBinding.framePolicy.

- LiveTestWidgetsFlutterBinding now defaults to using a frame policy
  that pumps slightly more frames, to animate the pointer crosshairs.

- Added "flutter run --use-test-fonts" to enable Ahem on devices.

- Changed how idle() works to be more effective in live mode.

- Display the test name in live mode (unless ahem fonts are enabled).

- Added a toString to TextSelectionPoint.

- Style nit fixes.

* Roll engine to get Ahem changes.

* Update tests for dartdoc changes.

* Fix flutter_tools tests

Nobody knew what a Block was.

Fixes https://github.com/flutter/flutter/pull/8643

Fixes https://github.com/flutter/flutter/issues/8804 by adding a test
to verify that Material elevation changes animate.

Also tweak some dartdocs, add some trailing commas, improve some
toString output, make the inkwell test agnostic to the PhysicalModel
logic, and move the material buttons test to the material test
directory.

Fixes https://github.com/flutter/flutter/issues/9031

Also some updates to mock_canvas that were needed to do this.

* Bump to Dart SDK 1.23.0-dev.10

* allows us to understand flutter usage via telemetry
* brings in `@immutable`

Fixes: #9042

* completer fix

* Update to platform 1.1.1.

This patch prepares us to remove InputValue in favor of TextEditingValue.

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.

Since RelativeRect's whole purpose in life is to make work with Stack
easier, it's silly that you can't directly use it with Positioned.

Also, tests for RelativeRect.
And fixes for the bugs that found...

All the clients have migrated to GridView.  Also, remove RenderGrid,
which isn't needed by GridView.

We weren't triggering a relayout when the number of children changed.

Fixes #8001

This patch passes down the viewportMainAxisExtent so that RenderSliverPage can
pick it up and size its children appropriately.

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

This patch adds grid supports to slivers and introduces a ScrollGrid
convenience class for making the common types of scrollable grids.

This patch also deploys ScrollGrid in an example in the Flutter Gallery.

Add SliverList

A SliverList is a linear layout of box children in a viewport that all
have a common, fixed extent along the scroll axis. The layout is similar
to a SliverBlock but more efficient.

The needsLayout getter is prone to misuse. See discussion on #3083.

When you put a box in a Viewport2, it might paint outside its allocated bounds.
This patch teaches Viewport2 to clip when that happens.

I plan to use this to implement similar logic in SliverPadding.

To make this easier to test I extended the paints matcher to accept a
function that takes a canvas. While I was at it I also made it accept
a Finder, it'll go and find the render object for you.

Also added support for paints..path and fixed some grammar in the
error messages.

Also improved the docs for debugPaint*.

This widget is a replacement for ScrollableViewport that uses the new
Scrollable2 machinery. The widget is not based on Slivers but does use the new
scroll behavior classes.

Teach `paints` matches about `drawRect` and how to `paintChild`.

Also, improve test coverage.

This will make it easier to understand what this file does.

MockCanvas to use it instead.

Currently it only supports a very limited set of drawing features, but
adding new ones is easy.

Once the feature set is more complete, and we've used this a bunch, if
it feels right, this API will get promoted to flutter_test.