See https://github.com/flutter/flutter/pull/18881#discussion_r199285256

Our first step towards https://github.com/flutter/flutter/issues/18727

* Bump mockito to 3.0.0-beta

* Few fixes

* fix test

* Bump image

* Fix

* New packages update

* With matcher pinned

* No more typed

The new matcher package deprecates isInstanceOf which seems eggregious.

* Revert "Revert "Move mockito to 3.0.0-alpha. (#15949)" (#15979)"

This reverts commit e59651f9.

* More thenReturn to thenAnswer when mocking Futures

* Revert "More thenReturn to thenAnswer when mocking Futures"

This reverts commit 194d2cf41754ad171efd6bb5898cf73bce5a75ab as we are reverting engine roll.

* Revert "Revert "More thenReturn to thenAnswer when mocking Futures""

This reverts commit 52c9e96b304b220f66d78a252fccea0c8e0ef24c.

* Add dependency override

* Fix issue

Type-related fixes in flutter_driver and fuchsia_remote_debug_protocol
tests.

This caused a test failure in the integration_ui_ios devicelab test.

```
stdout: [   +3 ms] 00:02 [32m+0[0m: end-to-end test Ensure keyboard dismissal resizes the view to original size[0m
stdout: [+8129 ms] 00:11 [32m+0[0m[31m -1[0m: end-to-end test Ensure keyboard dismissal resizes the view to original size [1m[31m[E][0m[0m
stdout: [   +5 ms]   DriverError: Failed to fulfill Tap: Flutter application not responding
stdout: [        ]   Original error: TimeoutException after 0:00:07.500000: Future not completed
stdout: [        ]   Original stack trace:
stdout: [        ]   #0      FlutterDriver._sendCommand (package:flutter_driver/src/driver/driver.dart:324:18)
stdout: [        ]
stdout: [        ]   #1      FlutterDriver.tap (package:flutter_driver/src/driver/driver.dart:368:11)
stdout: [        ]
stdout: [        ]   #2      main.. (file:///[... snip ...]/flutter/dev/integration_tests/ui/test_driver/keyboard_resize_test.dart:34:20)
```

This reverts commit 067be92a.

Roll engine to version dd6f46c485192f4506035088c9065b9f5dbba9ab

* All lists produced by JSON parsing are List<dynamic>. If more
speficic type is required then they need to be explicitly cast, e.g.
using castFrom helper;
* Function of type (ByText) -> Finder is not a subtype of
(SerializableFinder) -> Finder because ByText is in the contravariant
position;
* In Dart 2 typed(any) should be used instead of any in mockito based
tests.

* Change async stubbing to use thenAnswer.

Mockito now prohibits calling thenReturn with Futures and Streams. dart-lang/mockito#79

* Update all Mockito deps to 3.0.0.

* Revert "Update all Mockito deps to 3.0.0."

This reverts commit e8ab9d37c33d3d7fe384abde64ea5b4d72623c75.

I did not correctly update the mockito dep, and there's no easy way to update to 3.0 alpha right now.

* Change thenAnswer((_) => to thenAnswer((invocation) =>

* Add Invocation type to thenAnswer lambdas

This patch reorganises flutter_driver's lib/src directory into three
subdirectories:

* driver: sources transitively imported/exported by flutter_driver.dart,
  which defines the API used by driver tests executed on the host machine.

* extension: sources transitively imported/exported by
  driver_extension.dart, which defines the API used to instrument a
  Flutter app running on the target device for use with a driver test.

* common: sources common to both driver and extension code.

This makes rolling Flutter into repositories that use Bazel (or
Bazel-like build systems) significantly more robust, due to the simpler
glob patterns involved.

Use of this file was eliminated in e7657b94.

* clear timeline events prior to starting a new action

* trailing commas

1. We want to measure wall-clock duration for the benchmarks, as opposed
   to thread duration (e.g., waiting on a mutex should accrue time) and
   'dur' is the metric to use for that.

2. On Darwin-based systems (macOS and iOS) 'tdur' is the result of a
   mach syscall lookup to thread_info. This call returns unreliable data
   on iOS. Chromium, for example, disables thread time support entirely
   for iOS.

This roll caused performance regressions in benchmarks:
* complex_layout_scroll_perf
* flutter_gallery_transition_perf

This reverts commit f430a45a.

* Roll engien to 79332e5c42555875c7070c33810dab3f0012ace1

* Remove deprecated @proxy

* Roll engine to ceb6d05c2fb3bd5c31a25d4b08be9fd97b55a446

The main purpose of this PR is to make it so that when you set the
initial route and it's a hierarchical route (e.g. `/a/b/c`), it
implies multiple pushes, one for each step of the route (so in that
case, `/`, `/a`, `/a/b`, and `/a/b/c`, in that order). If any of those
routes don't exist, it falls back to '/'.

As part of doing that, I:

 * Changed the default for MaterialApp.initialRoute to honor the
   actual initial route.

 * Added a MaterialApp.onUnknownRoute for handling bad routes.

 * Added a feature to flutter_driver that allows the host test script
   and the device test app to communicate.

 * Added a test to make sure `flutter drive --route` works.
   (Hopefully that will also prove `flutter run --route` works, though
   this isn't testing the `flutter` tool's side of that. My main
   concern is over whether the engine side works.)

 * Fixed `flutter drive` to output the right target file name.

 * Changed how the stocks app represents its data, so that we can
   show a page for a stock before we know if it exists.

 * Made it possible to show a stock page that doesn't exist. It shows
   a progress indicator if we're loading the data, or else shows a
   message saying it doesn't exist.

 * Changed the pathing structure of routes in stocks to work more
   sanely.

 * Made search in the stocks app actually work (before it only worked
   if we happened to accidentally trigger a rebuild). Added a test.

 * Replaced some custom code in the stocks app with a BackButton.

 * Added a "color" feature to BackButton to support the stocks use case.

 * Spaced out the ErrorWidget text a bit more.

 * Added `RouteSettings.copyWith`, which I ended up not using.

 * Improved the error messages around routing.

While I was in some files I made a few formatting fixes, fixed some
code health issues, and also removed `flaky: true` from some devicelab
tests that have been stable for a while. Also added some documentation
here and there.

For measuring the Dart thread, we care about thread duration (tdur) rather than
wall duration (dur) because we don't want to count the time when the Dart
thread is descheduled (e.g., in preference to the raster thread).

Prior to this change, these benchmarks were mostly measuring whether the OS
decided to finish the Dart thread's time slice or hand over the CPU to the
raster thread to complete the visual part of the frame. Now we actually measure
the work done on the Dart thread.

* disables all `flutter test` and `flutter drive` tests on Windows as those two commands are not fully implemented on Windows yet
* fixes other failures on Windows

This remove a very brittle aspect of flutter drive, whereby it would
assume a known port instead of explicitly finding out what it was.

Fixes #7692 and hopefully fixes the devicelab tests.

As per the recent fix to the `always_specify_types` lint (https://github.com/dart-lang/linter/issues/199), literal maps and lists are now expected to be explicitly typed.

Running that lint on the repo identifies quite a few spots to update.  This focuses on `flutter_driver` and `flutter_sprites` (somewhat arbitrarily) but the changes are fairly representative.

Note there are a number of places where I made a quick judgement on how specific to make the types.  Feedback on those is welcome.  (Especially as we move forward with more.)

*  Gallery demo start-time performance test