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.

* don't resolve symlinks as part of which

* update method dartdoc

Changed the ExpandIcon constructor to take a default expansion state.
If the widget gets rebuilt with a different expansion value, the
animation will trigger but the callback will not.

Do not throw when resolving a local engine if the .packages map does not include the flutter package (#5519)

TBR

Alternative PowerShell script. Fix missing pop in BAT file (in case of fatal error). Exit gracefully. Force SDK Path. (#5484)

The type of rejects should be List<dynamic> to match the type that
DragTarget expects. Since the function doesn't use rejects anyway,
there's no need to tighten the type.

Fixes one of the strong_mode_static_type_error errors that is currently
being ignored.

Added a widget that implicitly animates the size of it child.

Added a widget that automaitcally rotates the expansion icon and
offers a callback interface that captures presses.

Using IconButton inside of a bigger Material before would result
in having a hit box as large as the whole Material. This commit
constrains the size of the hit box and splashes to the default
diameter of a splash.

Fixes https://github.com/flutter/flutter/issues/5462

@mpcomplete

Fixes https://github.com/flutter/flutter/issues/5468

Currently, we just treat Fuchsia as TargetPlatform.android, but we might
want to do something more sophisticated in the future.

These tests should hit some previously untested lines.

This commit changes MergeableMaterial to include a flag that
specifies whether connected Material slices should have dividers
between them.