Previously, it was unclear that the middle slider was disabled.

Fixes #5517

Fixes https://github.com/flutter/flutter/issues/5283

Other changes in this patch:

Rename OffStage to Offstage.
Fixes https://github.com/flutter/flutter/issues/5378

Add a lot of docs.

Some minor punctuation and whitespace fixes.

1: If a route is already dismissed when it's popped, there's no point
trying to animate heroes, because it's going to be gone before the
heroes code can look at it.

2: If a hero animation finishes just as a new one is starting, we
previously blew away the state for the starting one. Now we correctly
segregate the "starting up quest" variables from the "actively ongoing
quest" variables.

Added ExpansionPanel and ExpansionPanelList. The implementation
is based on the Material design spec, without enforcing every
facet of it, leaving the developer using this the liberty to
enforced it lower down the widget tree. This decision was made
based on the argument that implementing more of the spec would
reduce flexibility to a point where some design would not be
implementable with this widget anymore.

Somehow we missed this before.

Fixes https://github.com/flutter/flutter/issues/5615

Fixes https://github.com/flutter/flutter/issues/5588

* implement flutter packages get/upgrade command
* alias flutter pub
* refactor findProjectRoot for use by multiple commands

fixes https://github.com/flutter/flutter/issues/4994

This change adds a top-level getBuildDirectory func and funcs for
android, aot, asset, ios build products.

Developers may now add a "build-dir" mapping to their
~/.flutter_settings (JSON format) config file. Output directory is
relative to the main flutter application directory.

This change also changes the default build directory for iOS builds to a
subdirectory of the configured build directory, 'build/ios' by default.

* add flutter channel command
fixes https://github.com/flutter/flutter/issues/2513

* fix test

* address comments

* remove unused imports

* fix lints

* enhance flutter upgrade to find project root
fixes https://github.com/flutter/flutter/issues/2990

* address comments

* restore original formatting

* fix lints

has been fully processed before completing the returned future.
This helps prevent tests that rely on stdout from being flaky.

Doesn't do any of the fancy effects. Just lets the user control the
back transition by sliding from the left, like a drawer. Hero
transitions are disabled during the gesture.

BUG=https://github.com/flutter/flutter/issues/4817

This reverts commit 09e68c33.

AOT snapshotter is broken at this engine rev.

https://flutter-dashboard.appspot.com/api/get-log?ownerKey=ahNzfmZsdXR0ZXItZGFzaGJvYXJkclgLEglDaGVja2xpc3QiOGZsdXR0ZXIvZmx1dHRlci8wOWU2OGMzM2NjZGIzNTVmZWRkNzVhODcxNmRlMDU1MWM3NzJmMmRlDAsSBFRhc2sYgICAgICAwAgM

Change the Gallery sample Android package to not conflict with the version published in Play (#5579)

Add update dialog to gallery, open source part of #4626

`Process.start` seems to be escaping as needed.

* test flutter create project dart file is properly formatted

* restore driver-test

* cleanup lint warnings

* address comment

Previously, `flutter build` products were emitted to build/ and only
xcode build products were emitted to $SYMROOT.

If the input test script contains a bad import, sky_shell will fail to
execute main(), in which case a connection to /runner is never
established and the _ServerInfo.socket never completes.

This change works around this by issuing a request on /shutdown when
sky_shell exits.