* Unpin package:test and upgrade packages

* Update packages/flutter/test/foundation/stack_trace_test.dart

* Also add packages/flutter_tools/test/data/asset_test/font/.dartignore to ensure that update-packages --force-upgrade does not crash.

* Escape path separator in regexps

* Update platform_helper.dart

* Update stack_trace_test.dart

* Update stack_trace_test.dart

Seems like we don't yet run the flutter tests on Windows, but we're
close to being able to. This makes some minor changes to make that
more possible:

 - fix the stack parsing code to support Windows paths
 - fix the tests for the stack error handling code to handle Windows paths
 - skip some tests that rely on Ahem font metrics

Fixes https://github.com/flutter/flutter/issues/10695

...instead of the engine.

This allows the scheduler library to depend on the services library
and the painting library to depend on the scheduler library without
the services library having to depend on the scheduler library.

While I was at it I also cleaned up some of the binding logic: the
licenses logic can now be overridden (and the test library does so),
and the image cache can now be overridden as well.

Make regular Alignment values look more like enumProperties while
leaving more complex AlignmentDirectional values unchanged.

(I suspect this accounts the sets of microtasks from scheduleWarmUpFrame now running separately.)

Issue https://github.com/flutter/flutter/issues/9998

* enable lint prefer_foreach

* fix tests

Diagnostics object is.

* Semantic hit test order for Slivers

* ++

* fix double space

* refactoring

* fix test

* comment fix

* tests

* remove accidental debugDumpSemanticsTree

* review comments

* fix button

Bare bones widget inspector support.

Toggle the widget inspector from the flutter tool by pressing 'i'.
When the widget inspector is select mode:
Pointer down to to inspect a widget.
Pointer click to finalize selection of a widget. You can now interact
with the application as you normally would but with the inspected widget
highlighted.
Click the inspect icon in bottom left corner of screen to reactivate
select mode.

It was previously possible for event dispatch to occurr during the
brief window where the tree had been marked dirty but before it had
been relaid out by reassemble, which would cause assertions to fire if
someone did a hot reload while touching the device.

Add Diagnosticable base class and documentation

* add a profile() method

* add todos

This reverts commit 4b4cabb7.

* fire service protocol extension events for frames

* start time in micros

* introduce a profile() function; only send frame events when in profile (or debug) modes

* moved the profile() function to foundation/profile.dart

* refactor to make the change more testable; test the change

* fire service protocol events by listening to onFrameInfo

* remove the frame event stream; add a devicelab test

* remove a todo

* final

It was 8.0. It's now arbitrarily 18.0.

Changing this required adjusting some tests. Adjusting the tests
required debugging the tests. Debugging the tests required some tools
to help debugging gesture recognizers and gesture arenas, so I added
some. It also required updating some toString() methods which resulted
in some changes to the tree diagnostics logic.

Also I cleaned up some docs while I was at it.

Refactor RenderObject.toStringDeep and Widget.toStringDeep code to use DiagnosticsNode.

* Switch existings tests to use equalsIgnoringHashCodes and add more tests.

* Revert "Revert "Change all ocurrences of '$runtimeType#$hashCode' to use the idAndType method. (#10871)" (#10880)"

This reverts commit ceb814aa.

Revert "Change all ocurrences of '$runtimeType#$hashCode' to use the idAndType method. (#10871)" (#10880)

This reverts commit d46e208b.

* Change all instances of '$runtimeType#$hashCode' to use the describeIdentity method.

The describeIdentity method generates a shorter description with a consistent length
consisting of the runtime type and the a 5 hex character long truncated
version of the hash code.

* Add more tests of toStringDeep.

These tests will help ensure toStringDeep behavior is not regressed
by refactoring toStringDeep to support structured data.

* expose debugPaintBaselinesEnabled

* Update binding.dart

review comments

Requires https://github.com/flutter/engine/pull/3688

This splits the frame pipeline into two, beginFrame and drawFrame.

As part of making this change I added some debugging hooks that helped
debug the issues that came up:

 * I added debugPrintScheduleFrameStacks which prints a stack whenever
   a frame is actually scheduled, so you can see why frames are being
   scheduled.

 * I added some toString output to EditableText and RawKeyboardListener.

 * I added a scheduler_tester.dart library for scheduler library tests.

 * I changed the test framework to flush microtasks before pumping.

 * Some asserts that had the old string literal form were replaced by
   asserts with messages.

I also fixed a few subtle bugs that this uncovered:

 * setState() now calls `ensureVisualUpdate`, rather than
   `scheduleFrame`. This means that calling it from an
   AnimationController callback does not actually schedule an extra
   redundant frame as it used to.

 * I corrected some documentation.

* upgrade to linter-0.1.30

* add prefer_is_empty lint
* add directives_ordering lint
* add no_adjacent_strings_in_list lint
* add no_duplicate_case_values lint
* add prefer_collection_literals lint
* add prefer_const_constructors lint
* add prefer_contains lint
* add prefer_initializing_formals lint
* add unnecessary_null_aware_assignments lint
* add unnecessary_null_in_if_null_operators lint

Aggressively apply the const lint.

We now have an explicit focus tree that we manage. Instead of using
GlobalKeys to manage focus, we use FocusNode and FocusScopeNode objects.
The FocusNode is Listenable and notifies when its focus state changes.

Focus notifications trigger by tree mutations are now delayed by one
frame, which is necessary to handle certain complex tree mutations. In
the common case of focus changes being triggered by user input, the
focus notificiation still arives in the same frame.