* Roll engine to b6df7a637498ca9beda1fa9cd7210e3202ea599f.
Changes since last roll:
```
b6df7a637 Roll dart to 290c576264faa096a0b3206c71b2435309d9f904. (#4771)
a6764dbd5 Add sources for Fuchsia target. (#4763)
2d5900615 [fuchsia] Remove unused header file. (#4769)
9717063b7 Revert "Roll dart to c080951d45e79cd25df98036c4be835b284a269c. (#4767)" (#4768)
9a9814312 Roll dart to c080951d45e79cd25df98036c4be835b284a269c. (#4767)
e74e8b35c [async] Update includes of async headers to new path (#4760)
e2c4b2760 Use Dart 2 camel case constants in the engine Dart libraries (#4766)
9c1e48434 Updates for Fuchsia roll. (#4765)
14c940e27 Switch from fxl::Mutex to std::mutex (#4764)
debf82c0b Roll Garnet (#4759)
5bffdefbb Use weak pointers to the accesibility bridge from objects vended to the UIKit accessibility framework. (#4761)
```
* only tap on widgets reachable by hit testing
* use FractionalOffset
* added tests
* check finder finds correct widget
* undo unintentional changes
* address comments
* style fix
* add Directionality in test
* fix analysis warning
* Revert "Make plugins add their repos to projects in the consuming app (#11447)"
This reverts commit abe1e2520b.
* Revert "Support for custom build types on Android (#11354)"
This reverts commit 87eec719e2.
* Revert "add a profile() method (#11443)"
This reverts commit 561d17a876.
* Revert "Fix documentation based on dartdoc's warnings (#11428)"
This reverts commit 6655074b37.
* Revert "Improve some docs around WillPopScope. (#11429)"
This reverts commit 58a28a2965.
* Revert "temporarily disable broken driver test in integration_ui (#11440)"
This reverts commit 764515ec78.
* Revert "style fix"
This reverts commit 00bfc86630.
* Revert "tests for waitFor/waitForAbsent"
This reverts commit 31d2ee9c0c.
* Revert "Always evaluate the finder in `driver.waitFor()` and `driver.waitForAbsent()`"
This reverts commit 11d7c79b99.
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.
Adds an initial integration test that:
1. captures laid-out widget size
2. focuses a text field to show the keyboard and resize the view
3. unfocuses the text field to dismiss the keyboard and resize the view
4. verify that the final widget size matches the initial size
