Remaining known issues are #10831 and #10830.

* more widget const constructors

* prefer const constructors

* address review comments

* make @immutable const

* fix build

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

Aggressively apply the const lint.

* use color.shadeXxx instead of color[Xxx]

* remove calls to .shade500 on MaterialColor

* remove calls to .shade200 on MaterialAccentColor

* fix test

This machinery is useful for arbitrary boxes (e.g., with FittedBox).

Fixes #6463

The new name follows the pattern of the name suggesting which layout
protocol the parent expects the child to speak.

Fixes #8664

The replacements are ListView and SingleChildScrollView, respectively.

Move the back button and drawer opening logic into the app bar.

Move the tap-status-bar-to-scroll-to-top logic to using
ScrollControllers. Provide a PrimaryScrollController and a `primary`
flag on scroll views.

Make it possible to track when a route becomes or stops being poppable.

Someone on stack overflow was mutating the list of recipes and getting
confused about why the UI didn't redraw. Making kPestoRecipes a constant
might help avoid that confusion.

This patch replaces uses of Flexible with Expanded where we're using
FlexFit.tight. We still need to think of a better name for the
FlexFit.loose variant.

Also, improve the docs for Row, Column, Flex, and RenderFlex to be more
problem-oriented and to give a complete account of the layout algorithn.

Fixes #6960
Fixes #5169

Fixes https://github.com/flutter/flutter/issues/6561

Since we can change the theme's platform, we need to make sure we
propagate that throughout rather than having half the app use the native
platform and half the app use the selected platform.

The current implementation matches the default behaviour of the material
scaffold.

* Changed Pesto logotype's position.

This commit changes Pesto's logotype position so that its curve
aligns with the curve of the image size.

* Added clamping to Pesto logo animation.

Fixes https://github.com/flutter/flutter/issues/5711

Removed Pesto logo's triggered animation in order to remove the
observable 'hop' when scrolling. The whole curve is now entirely
scroll dependent. Fixes #5907.

Due to a synchronization issue, a PR was merged with a green build
that was supposed to be rebuilt and to fail. This commit fixes the
issue by renaming the usage of a constant.

Fixes https://github.com/flutter/flutter/issues/5684

* Added OverscrollIndicatorEdge et al

* RefreshIndicator only clamps its scrollable edge

* added a test

* Updated the test

* fixed lint-os

* fixed a typo

* Scrollable should restore its viewport dimensions when it reappears

* removed an accidental commit

* updated per review feedback

The drawer was confusing without adding much value. It was
especially confusing when wanting to go back to the Gallery on iOS.
Fixes #5713.

BUG=https://github.com/flutter/flutter/issues/5351

The floating action button inside of the Pesto demo now opens up
a snackbar. Fixes #5685.

Fixes https://github.com/flutter/flutter/issues/5462

@mpcomplete

BUG=https://github.com/flutter/flutter/issues/5098

This patch improves the Post and Shrine transitions by making the AppBar
into a Hero and changing the default MaterialPageTransition. Now the
AppBar transitions smoothly between screens and the
MaterialPageTransition doesn't involve a fade effect.

Also, rejigger the bounds of the image header in Pesto to avoid the
"pop" at the end of the animation by laying out the image header at its
final visual size instead of relying on occlusion to size the image
header.

Fixes #5202
Fixes #5204