Animate TwoLevelList leading icon color

Add keys to ResourceImages.

[driver] fix observatory port # and timeline data extraction

The way we pick observatory port # has changed and we have broken
logic that handles port 8181. To fix the buildbot, switch to port
8182. We can later figure out what we want to do when we clean up
port handling.

The old VM extention for extracting the timeline data is gone.
Switch to the new '_getVMTimeline' API.

Use _ScaffoldLayout to position scroll-resizable appbars

Table widget

- Add x and y to the parent data, in case it's useful. In point of fact,
  I ended up not needing it.

- Make columnWidths settable rather than having a setter so that the
  code in the widgets layer is more idiomatic.

- Teach setFlatChildren about avoiding unnecessary drop/adopt loops.

- Assert that the child list length is correct more aggressively so that
  we catch the dumb bug I had more quickly next time.

- Improve the toString() to handle empty tables better.

- Resort the imports in framework.dart.

- Introduce a LocalKey for cases where you don't want to allow use of
  GlobalKey.

- Make inflateWidget and deactivateChild public for subclass use.

- Table widget.

- Cell widget.

- TableRow fake widget.

Allow Draggables to drop through DragTargets that don't accept them to one that does.

adjust upgrade command

Fix fullscreen dialog gallery example

More elaborate exceptions.

AnimatedOpacity

This provides an easy way to do implicit opacity transitions.

The elaboration will continue until morale improves.

Specific exceptions considered here:

 - size setter checking when you set the size
 - layout verifying that you do set the size
 - hitTest verifying that you aren't dirty and have a size
 - flex complaining about canFlex

Adds constants for FractionalOffsets

Adds some names for common FractionalOffset values.

Pointer events should pass buttons through

Fixes #2899

Remove two `flutter analyze` regular expressions

Update test.sh

fix an exception from flutter doctor

We can work around these in code rather than by post-processing the analyzer
output.

[driver] propagate exit code from package:test

Driver returns exit code 0 even when tests fail. This commit fixes it by
propagating the exit code set by `package:test`.

Use --packages rather than --package-root

The .packages file is replacing the packages directory of symlinks.

ChildView throws exceptions outside MojoShell

Rename debugOwner to debugCreator

Fixes #2940

`flutter upgrade` needed twice if sky_services dependencies change

Now we run `flutter --version` to update our local cache of packages before
running `pub upgrade`, which reads from that cache.

Fixes #2953

We're missing a null check.

Fixes #2949