* added sample code for scaffold widget [#21136]

* Fixed indent and spacing for scaffold sample code

* Update scaffold.dart

Fix one more formatting issue

Previously flutter_tools had used "gradle properties" to find the build types
and flavors supported by the Gradle project.  Tasks should work more reliably
across different versions of the Android Gradle plugin.

Fixes https://github.com/flutter/flutter/issues/20781

* Adding Changelog URL to the README.md file

* Update README to match the latest version on DEV

- Update README to match the latest version on DEV branch 
- Add Changelog URL

* Update README.md

Fix contributing link

This reverts commit ec0df111.

https://github.com/flutter/engine/compare/74662ab69523...7e3b41dc7ba6

git log 74662ab69523..7e3b41dc7ba6 --no-merges --oneline
7e3b41dc7 Roll src/third_party/skia 08417bccf256..bfa76f20bfcf (4 commits) (flutter/engine#6416)
69ae5694d Do not register UI-related native functions in secondary isolates (flutter/engine#6401)
19c135c67 Roll src/third_party/skia b627af80e3a4..08417bccf256 (8 commits) (flutter/engine#6415)
65b886ba9 Roll src/third_party/skia be8193c9313a..b627af80e3a4 (1 commits) (flutter/engine#6414)
360d44668 Use single_root_scheme when compiling platform (flutter/engine#6402)
c7a5abf98 Roll src/third_party/skia deb512045e6a..be8193c9313a (1 commits) (flutter/engine#6413)

The AutoRoll server is located here: https://autoroll.skia.org/r/flutter-engine-flutter-autoroll

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.

* Revert "Custom offset functionality for Popup Menu Button (#22534)"

This reverts commit f44b277f.

* Revert "Updated the ColorScheme dartdoc: a11y (#22618)"

This reverts commit aa6a27e8.

* Revert "Added support for the Khmer (km) language (#22617)"

This reverts commit 3a87b93f.

* Revert "Use 'Future<void>' insted of 'Future<Null>' in SystemChrome (#22583)"

This reverts commit 37c10acb.

* Revert "Choice Chip Fix (#22589)"

This reverts commit 8d76d37f.

* Revert "Throw if trying to set fs.currentDirectory in tests (#22037)"

This reverts commit 2f6155bf.

* Revert "Use (processors-1) for test runs (test defaults to processors/2) (#22085)"

This reverts commit d44f0030.

The only reds on the dashboard for this test are on rows that have many failures across the run; this does not appear to be at all flaky.

* Adds offset functionality to popup menu
* Adds a test

* choice chip fix

* added test

* Block setting of fs.currentDirectory in tests

This isn't perfect, it only covers tests using testUsingContext, but that is the huge majority of tests.

* Tweak error message.

* Use (processors-1) for test runs (test defaults to processors/2)

* Add missing import 🙄

https://github.com/flutter/engine/compare/f6af1f20ba92...74662ab69523

git log f6af1f20ba92..74662ab69523 --no-merges --oneline
74662ab69 Revert "Share engine layers with the framework" (flutter/engine#6412)
2de87a80f Roll src/third_party/skia 6719fcc43b1e..deb512045e6a (7 commits) (flutter/engine#6411)
68a42e3f4 Add nullability annotations to MethodChannel/MethodCall. (flutter/engine#6393)
71ba20a64 Dart SDK roll for 2018-10-02 to d2c5a24fd9ead97a7f18d02786e679293cc3709e (flutter/engine#6410)
9ccc96625 Share engine layers with the framework (flutter/engine#6406)
fa719e3e7 Roll src/third_party/skia cc4dbfcfbd8a..6719fcc43b1e (17 commits) (flutter/engine#6409)
dc2634dcf Force lf-line endings for so that source offsets match across platforms. (flutter/engine#6408)
44a514943 Roll src/third_party/skia 7dae882574d2..cc4dbfcfbd8a (15 commits) (flutter/engine#6405)
de32c659b Roll src/third_party/skia 3b8b11e1f912..7dae882574d2 (15 commits) (flutter/engine#6403)
3a9c22afd Allow GetRectsForRange to provide more detailed/nuanced metrics through RectStyle enum. (flutter/engine#6335)
b59c86493 Rename the Android fragment support library JAR (flutter/engine#6400)
4213ac19c Add an Android fragment support library to third_party (flutter/engine#6384)
a785b25f4 do not count Hidden nodes at the beginning of the scrollable (flutter/engine#6381)

The AutoRoll server is located here: https://autoroll.skia.org/r/flutter-engine-flutter-autoroll

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.

Merging on read to unbreak the build.

TBR= @Hixie 

Introduce an overall material "color scheme" and to make it possible to redefine how a component's visual properties bind to the color scheme and to the existing material Theme.

Add 'restoreSystemUIOverlays' to SystemChrome to allow simple UI restore after System force changes. (#22221)

* Add 'restoreSystemUIOverlays' to SystemChrome to allow simple UI restore after System force changes.

* use RadioListTile in expansion panels demo

Fixes #6048.
- expose `_Location`
- appease analyzer

* Change file paths to URIs to fix "Could not run configuration in engine" on Windows

Plus unskip test that was failing due to this.

Fixes #21348.

* Remove unused import

* Revert "unnecessary this in field initializers (#22522)"

This reverts commit 5de96bb7.

* Revert "Use unsafePackageSerialization when running tests (#22407)"

This reverts commit 4bd6ad73.

* Revert "Roll engine f6af1f20ba92..b59c86493159 (3 commits) (#22538)"

This reverts commit 85a4591a.

https://github.com/flutter/engine/compare/f6af1f20ba92...b59c86493159

git log f6af1f20ba92..b59c86493159 --no-merges --oneline
b59c86493 Rename the Android fragment support library JAR (flutter/engine#6400)
4213ac19c Add an Android fragment support library to third_party (flutter/engine#6384)
a785b25f4 do not count Hidden nodes at the beginning of the scrollable (flutter/engine#6381)


The AutoRoll server is located here: https://autoroll.skia.org/r/flutter-engine-flutter-autoroll

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.

Manually roll the engine to the last good commit known to the
auto-roller.

git log 0c2b6dc6e339..f6af1f20ba92 --no-merges --oneline
f6af1f20b Roll src/third_party/skia e8e2bb1384ad..3b8b11e1f912 (4 commits) (flutter/engine#6395)
7f2e2ea4f Roll src/third_party/skia bba2921c1970..e8e2bb1384ad (1 commits) (flutter/engine#6394)
4f69beb27 Roll src/third_party/skia 7f3ceba5dc7f..bba2921c1970 (1 commits) (flutter/engine#6392)
a4a5449d5 Roll src/third_party/skia 22867ce6fe83..7f3ceba5dc7f (1 commits) (flutter/engine#6391)
31278f0b8 Roll src/third_party/skia ebfbf1d749c1..22867ce6fe83 (1 commits) (flutter/engine#6390)
73409c228 Roll src/third_party/skia 93d71666b2f1..ebfbf1d749c1 (1 commits) (flutter/engine#6389)
6f8c827b2 Dart SDK roll for 2018-09-28 (flutter/engine#6388)
6e96ae542 Roll src/third_party/skia cfa315390f04..93d71666b2f1 (6 commits) (flutter/engine#6386)
39dee5b61 Fix Fuchsia build. (flutter/engine#6383)
560eba1a3 Roll src/third_party/skia 87311c6e565f..cfa315390f04 (9 commits) (flutter/engine#6382)

The asset subsystem uses URIs to represent asset locations.  The font manifest
should also use URI-encoded paths instead of unencoded paths taken directly
from the manifest YAML.

Fixes https://github.com/flutter/flutter/issues/19452