Added a demo of BottomNavigation to the Gallery.

Switch our pubspec.yamls to using SDK sources so that we can have consistent
source types when we depend on these packages from external packages using SDK
sources.

The way this was implemented is sketchy, especially in strong mode.

Changed the fixed type to better support the dark theme.

Previously in some rather esoteric cases involving global keys reversing
relative positions we would forget to build everyone.

We changed how `flutter run --release` works (it quits without showing
logs now, since it can't tell when the app closes).

When switching from shifting to fixed, the BottomNavigationBar no
longer displays the old color of the background.

Cargo culted from http://stackoverflow.com/questions/24690739/nexus-5-galaxy-s5-and-some-other-devices-are-showing-not-compatible-in-google

This code is now in its own standalone library. The library is in a private git
repository in the flutter organization because the code is unmaintained. If
you're interested in using and maintaining this code, please contact
flutter-dev@googlegroups.com for more information.

This code is now in its own standalone library. The library is in a private git
repository in the flutter organization because the code is unmaintained. If
you're interested in using and maintaining this code, please contact
flutter-dev@googlegroups.com for more information.

Fixes #1364

* suppress warning; decouple the analyzer versions

* also pass in --no-packages-dir

* show hidden flags when showing verbose help
* flutter -v show verbose help

This structure for the API is hopefully less confusing that the previous one
(which implied that vertical drags would not trigger horizontally draggable
widgets).

Fixes #1987

This rewrites imports of various mojom.dart files from the Flutter
engine repo to instead import normal-looking dart files from the
(new) flutter_services package. This package handles exporting the
correct symbols from generated code wherever that may live.

Includes an engine roll to 3551e7a48e2e336777b15c7637af92fd7605b6c5
which contains the new flutter_services package.

Fixes https://github.com/flutter/flutter/issues/5973

These are the last dartdocs needed in the material library.

* 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.

It wasn't taking padding into account when deciding which children were
visible. I modeled the solution off of the way ScrollableList handles
this.

Fixes https://github.com/flutter/flutter/issues/5522

Adds unit test to verify the initial value of Input widgets.

For consistency with IconTheme and TextStyle.merge.

Fixes #4652

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.