This reverts commit 7ba775a9.

Avoid calling `builder` in `ConstrainedLayoutBuilder` when layout constraints are the same.

[Design doc](flutter.dev/go/layout-builder-optimization).

## Related Issues

Fixes https://github.com/flutter/flutter/issues/6469

Move Flutter Gallery to dev/integration_tests/ as it is an older copy used only for testing. The current version of the Flutter Gallery now lives in https://github.com/flutter/gallery.

* Update project.pbxproj files to say Flutter rather than Chromium

Also, the templates now have an empty organization so that we don't cause people to give their apps a Flutter copyright.

* Update the copyright notice checker to require a standard notice on all files

* Update copyrights on Dart files. (This was a mechanical commit.)

* Fix weird license headers on Dart files that deviate from our conventions; relicense Shrine.

Some were already marked "The Flutter Authors", not clear why. Their
dates have been normalized. Some were missing the blank line after the
license. Some were randomly different in trivial ways for no apparent
reason (e.g. missing the trailing period).

* Clean up the copyrights in non-Dart files. (Manual edits.)

Also, make sure templates don't have copyrights.

* Fix some more ORGANIZATIONNAMEs

This adds a canRequestFocus and skipTraversal argument to FocusScope and FocusScopeNode, so that a scope can prevent being traversed.

This allows a fix for a problem in the gallery where the focus while traversing the list of items would sometimes appear to disappear, since it would be focusing things that were in the backdrop that were part of the tree, but were not visible.

Related Issues
Fixes #42955

* 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

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

This will be needed once PhysicalShape sets the default clipBehavior
to Clip.none.

* Fixes resulting from audit of issues links

I looked at every link to GitHub in our repo. For cases where we had a TODO that was waiting for a bug to be fixed, and the bug has now been fixed, I applied the pending change. For cases where the link was out of date, I updated the link.

* Update run_test.dart

skip this test again since it failed on linux and macos bots

It was causing problems rolling Flutter into Fuchsia

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

* Give more room for the front layer drag on iPhone X

* Tweak the animation visual effects

* review lint

* Revert "New Flutter Gallery UI (#16936)"

This reverts commit 7038597b.