* 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

* fix some bad indentations

* remove suspicious line

This converts existing ## Sample code samples to {@tool sample}...{@end-tool} form.

Also:
1. Fixed a minor bug in analyze-sample-code.dart
2. Made the snippet tool only insert descriptions if the description is non-empty.
3. Moved the Card diagram to before the code sample.

* Future<void> main

* Future<void>.delayed

* prefer_void_to_Null

* address review comments

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

* lint unnecessary_new on samples

* fix tests

* Fix the confusing-zero case with NestedScrollView.

* Update mock_canvas.dart

* Update tabs_demo.dart

* more tweaks

* Fixed TrackingScrollController cleaning stored offset on position's detach

* Fixed format.

* Fixed format.

* Fixed test with Directionality support.

This reverts commit ec25f6bd.

* Fixed TrackingScrollController cleaning stored offset on position's detach

* Fixed format.

* Fixed format.

* Introduce a Directionality inherited widget which sets the ambient LTR vs RTL mode (defaulting to null, which means you cannot use directionality-influenced values).

* Make it possible to configure Padding (including Container.padding and Container.margin) using a directionality-agnostic EdgeInsets variant.

* Provide textDirection and verticalDirection controls on Row and Column to make them RTL-aware.

* Introduce a variant of FractionalOffset based on the EdgeInsets variant. Not yet actually used.

* Fix all the tests that depended on Row defaulting to LTR.

Mainly, this adds documentation to members that were previously
lacking documentation.

It also adds a big block of documentation about improving performance
of widgets.

This also removes some references to package:collection and adds
global setEquals and listEquals methods in foundation that we can use.
(setEquals in particular should be much faster than the
package:collection equivalent, though both should be faster as they
avoid allocating new objects.) All remaining references now qualify
the import so we know what our remaining dependencies are.

Also lots of code reordering in Flutter driver to make the code
consistent and apply the style guide more thoroughly.

* Revert "Revert "Change all ocurrences of '$runtimeType#$hashCode' to use the idAndType method. (#10871)" (#10880)"

This reverts commit ceb814aa.

Revert "Change all ocurrences of '$runtimeType#$hashCode' to use the idAndType method. (#10871)" (#10880)

This reverts commit d46e208b.

* Change all instances of '$runtimeType#$hashCode' to use the describeIdentity method.

The describeIdentity method generates a shorter description with a consistent length
consisting of the runtime type and the a 5 hex character long truncated
version of the hash code.

Introduce CompositedTransformTarget and CompositedTransformFollower
widgets, corresponding render objects, and corresponding layers.

Adjust the way text fields work to use this.

Various changes I needed to debug the issues that came up.

This reverts commit c8e4cbf2.

* preview of prefer_asserts_in_initializer_list lint

* fix issue

Previously, ScrollPosition did not know about ScrollActivities. However, all
the concrete subclasses of ScrollPosition that we know about need to use
ScrollActivities, so they ended up with a bunch of delegate boilerplate code.

This patch teaches ScrollPosition about ScrollActivities but doesn't have any
opinion about how to start or interact with those activities.

This patch is more refactoring to prepare for nested and linked scrolling.

This patch reworks some of the guts of scrolling to make it easier to
implement nested scrolling effects. The actually nested scrolling effect
will be included in a later patch.

This change make it easier to track the position of the scroll view without
having to worry about the position object changing out from under the
controller.

Also make locals final where possible.

Followup to 52715467.

* Improved defaults for scroll view primary-ness

* Vertical scroll views default to primary:true.
* Horizontal scroll views default to primary:false.
* If a scroll view is primary and it got a non-null inherited primary
  scroll controller, it introduces a primary scroll controller inherited
  with a value of null for its descendants.

ScrollController now multiplexes writes to all registered positions;
reads of position continue to assert that only one position is
registered. Reads still require a single position.

* More better toStrings and more vigorous smoke testing of gallery

* Update scroll_controller.dart

* Update sliver.dart