* Fix tests to use Ahem, and helpful changes around that

- Fix fonts that had metric-specific behaviours.

- LiveTestWidgetsFlutterBinding.allowAllFrames has been renamed
  to LiveTestWidgetsFlutterBinding.framePolicy.

- LiveTestWidgetsFlutterBinding now defaults to using a frame policy
  that pumps slightly more frames, to animate the pointer crosshairs.

- Added "flutter run --use-test-fonts" to enable Ahem on devices.

- Changed how idle() works to be more effective in live mode.

- Display the test name in live mode (unless ahem fonts are enabled).

- Added a toString to TextSelectionPoint.

- Style nit fixes.

* Roll engine to get Ahem changes.

* Update tests for dartdoc changes.

* Fix flutter_tools tests

* Rename `Device.platform` to `Device.targetPlatform` to avoid
  collision with the exported variable from `platform.dart`

Fixes #8209

* Add indent option to logger and indent non-flutter nested output

* Add a missed override

* Formatting

* improve the logger ui a bit for elapsed times

* invert param

* update daemon.dart

Move the drive/run common stuff to RunCommandBase, rather than the
superclass which applies to everything.

Implement --no-resident (fixes
https://github.com/flutter/flutter/issues/5448). This is particularly
useful when running flutter from scripts.

Rename RunAndStayResident to ColdRunner.

...and add --diagnostic-port.

...and document port 0.

...now that we have generic methods, their types need to be specified too.

* proxy service extension calls through the daemon protocol

* add test for app.callServiceExtension

* pass additional named params to daemon run

* add a trailing comma

This ensures that accidental usages of dart:io's
file API don't creep in over time.

This removes direct file access from within flutter_tools
in favor of using `package:file` via a `FileSystem` that's
accessed via the `ApplicationContext`.

This lays the groundwork for us to be able to easily swap
out the underlying file system when running Flutter tools,
which will be used to provide a record/replay file system,
analogous to what we have for process invocations.

* have flutter run --machine log to stdout

* add a test

* add docs; fix type annotation lint

* reapply handle new Observatory URL changes
Fixes https://github.com/flutter/flutter/issues/6843

* allow non numeric IPv4 addresses
Fixes https://github.com/flutter/flutter/issues/7051

https://github.com/flutter/flutter/commit/737a55ef3e47036220e72f3b3e17353d461b5fab

* Remove the workaround that pinned args to v0.13.6
This reverts most of the changes in commit 6331b6c8
* throw exception if exit code is not an integer
* rework command infrastructure to throw ToolExit when non-zero exitCode
* convert commands to return Future<Null>
* cleanup remaining commands to use throwToolExit for non-zero exit code
* remove isUnusual exception message
* add type annotations for updated args package

* convert flutter commands to use ToolExit for non-zero exit code
* add convenience method throwToolExit
* print ToolExit message iff not null

* make showElapsedTime default to true

* support nested progresses

* improve hot reload message

* rethrow

* add flutter run --machine flag
* refactor daemon stdin/out command stream/response
* extract daemon startApp method
* refactor flutter run --machine to call daemon.startApp

* add a pause parameter to the reload command

* encode OperationResult as json

* reverse isOk logic

* make app ids more unique

* in-line the uuid class