* Implement system fonts system channel listener

Reverting the last two engine rolls, since the first one caused an issue in the devicelab on 32-bit iOS devices.

* Revert "Roll engine e7fd442410f4..953ac71749ee (18 commits) (#41163)"
* Revert "Roll engine b875c7a5ff56..e7fd442410f4 (19 commits) (#41127)"

* Carrying last size and transform information to TextInputConnection. Doing this we are making sure that the size/transform information from the previous connection will be removed, when connection changes.

* remove unused lastsize and lasttransform values

* Adding unit tests. Adressing comments.

There were four or five different implementations in various tests for sendFakeKeyEvent, which roughly all did the same thing. I was going to add yet another one, and decided that it needed to be generalized and centralized. This replaces those instances with something that just takes a LogicalKeyboardKey so that it's self-documenting, and can be used with multiple platforms.

This adds two functions to widget tester: sendKeyDownEvent and sendKeyUpEvent which simulate key up/down from a physical keyboard. It also adds global functions simulateKeyDownEvent and simulateKeyUpEvent that can be called without a widget tester. All are async functions protected by the async guard.

git@github.com:flutter/engine.git/compare/e7fd442410f4...953ac71749ee

git log e7fd442410f4..953ac71749ee --no-merges --oneline
2019-09-24 bkonyi@google.com Roll src/third_party/dart acac9ab11b..d53d355c6c (12 commits)
2019-09-24 skia-flutter-autoroll@skia.org Roll src/third_party/skia b4b1005d485f..c096654fa7c6 (1 commits) (flutter/engine#12415)
2019-09-24 skia-flutter-autoroll@skia.org Roll src/third_party/skia b3542d95da65..b4b1005d485f (6 commits) (flutter/engine#12414)
2019-09-24 ueman@users.noreply.github.com Write MINIMAL_SDK to exception message (flutter/engine#11345)
2019-09-23 franciscojma86@gmail.com Track "mouse leave" event (flutter/engine#12363)
2019-09-23 bkonyi@google.com Roll src/third_party/dart 77ff89b223..acac9ab11b (6 commits)
2019-09-23 mouad.debbar@gmail.com Don't send pointer events when the framework isn't ready yet (flutter/engine#12403)
2019-09-23 aam@google.com Update test to verify that secondary isolate gets shutdown before root isolate exits. (flutter/engine#12342)
2019-09-23 skia-flutter-autoroll@skia.org Roll src/third_party/skia 57ef68077574..b3542d95da65 (12 commits) (flutter/engine#12409)
2019-09-23 bkonyi@google.com Update --dart-vm-flags whitelist to include --write-service-info and --sample-buffer-duration (flutter/engine#12395)
2019-09-23 47866232+chunhtai@users.noreply.github.com Add system font change listener for windows (flutter/engine#12276)
2019-09-23 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/mac-amd64 from xPX7p... to kgFwg... (flutter/engine#12405)
2019-09-23 garyq@google.com Check for index bounds in RTL handling for trailing whitespace runs. (flutter/engine#12336)
2019-09-23 skia-flutter-autoroll@skia.org Roll fuchsia/sdk/core/linux-amd64 from F-g18... to NY2A5... (flutter/engine#12407)
2019-09-23 bkonyi@google.com Roll src/third_party/dart f546362691..77ff89b223 (6 commits)
2019-09-23 50856934+nturgut@users.noreply.github.com Updating text field location in IOS as a pre-work for spellcheck (flutter/engine#12192)
2019-09-23 chinmaygarde@google.com Roll buildroot and remove toolchain prefix. (flutter/engine#12324)
2019-09-23 bkonyi@google.com Roll src/third_party/dart 94dd49cdb6..f546362691 (1 commits)


If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC stuartmorgan@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
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git@github.com:flutter/engine.git/compare/b875c7a5ff56...e7fd442410f4

git log b875c7a5ff56..e7fd442410f4 --no-merges --oneline
2019-09-23 skia-flutter-autoroll@skia.org Roll src/third_party/skia ab52a7a53db6..57ef68077574 (3 commits) (flutter/engine#12396)
2019-09-23 jaimeblasco97@gmail.com [Web] Implement dark mode support for web (flutter/engine#12335)
2019-09-23 bkonyi@google.com Roll src/third_party/dart 07f0bc0144..94dd49cdb6 (3 commits)
2019-09-23 skia-flutter-autoroll@skia.org Roll src/third_party/skia 776d81525e7c..ab52a7a53db6 (1 commits) (flutter/engine#12393)
2019-09-23 skia-flutter-autoroll@skia.org Roll src/third_party/skia 5b4c0ee19b74..776d81525e7c (1 commits) (flutter/engine#12392)
2019-09-23 bkonyi@google.com Roll src/third_party/dart 60c2bb9f5b..07f0bc0144 (7 commits)
2019-09-23 skia-flutter-autoroll@skia.org Roll src/third_party/skia b4d60b5eda31..5b4c0ee19b74 (1 commits) (flutter/engine#12390)
2019-09-23 skia-flutter-autoroll@skia.org Roll src/third_party/skia bd67d0035a80..b4d60b5eda31 (7 commits) (flutter/engine#12389)
2019-09-22 skia-flutter-autoroll@skia.org Roll src/third_party/skia 942d69fa9d5f..bd67d0035a80 (1 commits) (flutter/engine#12382)
2019-09-22 yjbanov@google.com Add macOS testing support (flutter/engine#12383)
2019-09-21 bkonyi@google.com Roll src/third_party/dart ff0e8f8035..60c2bb9f5b (5 commits)
2019-09-20 bkonyi@google.com Roll src/third_party/dart 70a1e8e090..ff0e8f8035 (18 commits)
2019-09-20 skia-flutter-autoroll@skia.org Roll src/third_party/skia 2e29ab5b03aa..942d69fa9d5f (6 commits) (flutter/engine#12378)
2019-09-20 yjbanov@google.com Store screenshot test output as Cirrus artifacts; do fuzzy comparison of non-matching screenshot pixels (flutter/engine#12274)
2019-09-20 30870216+gaaclarke@users.noreply.github.com Added unit tests for method channels. (flutter/engine#12373)
2019-09-20 jason-simmons@users.noreply.github.com Roll Wuffs to 0.2.0-alpha.47 (flutter/engine#12376)
2019-09-20 dnfield@google.com Sync dart_runner (flutter/engine#12375)
2019-09-20 skia-flutter-autoroll@skia.org Roll src/third_party/skia ffdc3e668061..2e29ab5b03aa (12 commits) (flutter/engine#12374)
2019-09-20 bkonyi@google.com Roll src/third_party/dart 7c1821c4aa..70a1e8e090 (52 commits)


If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC stuartmorgan@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
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Documentation for the AutoRoller is here:
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Fixes #41144
Merge on red to fix builds.

* Unit test for build.dart::GenSnapshot

* Fix analysis errors

* Switch to testLogger

git@github.com:flutter/engine.git/compare/99092a0436a2...b875c7a5ff56

git log 99092a0436a2..b875c7a5ff56 --no-merges --oneline
2019-09-20 ditman@gmail.com Add web engine screenshot (scuba) tests (flutter/engine#12353)
2019-09-20 skia-flutter-autoroll@skia.org Roll src/third_party/skia 9a9841178078..ffdc3e668061 (1 commits) (flutter/engine#12369)


If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC stuartmorgan@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
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Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

This reverts commit 96482eeb.

This reverts commit b12bdd0e as it
breaks existing tests that expect image loaded after certaing number of
pupms. With image loading done on separate isolate pumping is not
guaranteed to get image loaded.

git@github.com:flutter/engine.git/compare/70f21b0edb06...99092a0436a2

git log 70f21b0edb06..99092a0436a2 --no-merges --oneline
2019-09-20 skia-flutter-autoroll@skia.org Roll src/third_party/skia be0d7dfa6194..9a9841178078 (2 commits) (flutter/engine#12368)
2019-09-20 skia-flutter-autoroll@skia.org Roll src/third_party/skia e5b65d212bca..be0d7dfa6194 (3 commits) (flutter/engine#12367)
2019-09-20 liyuqian@google.com Revert "Reland "Smooth out iOS irregular input events delivery (#11817)" (#12280)" (flutter/engine#12364)
2019-09-20 skia-flutter-autoroll@skia.org Roll src/third_party/skia f47717ad8cc7..e5b65d212bca (4 commits) (flutter/engine#12366)


If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC stuartmorgan@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

git@github.com:flutter/engine.git/compare/1cada0a6dca6...70f21b0edb06

git log 1cada0a6dca6..70f21b0edb06 --no-merges --oneline
2019-09-19 matthew-carroll@users.noreply.github.com Fixes race condition that was reported internally. (flutter/engine#12362)
2019-09-19 a-siva@users.noreply.github.com  Roll src/third_party/dart 7c1821c4aa...ea969c358e (flutter/engine#12339)
2019-09-19 skia-flutter-autoroll@skia.org Roll src/third_party/skia 9a8b846baf43..f47717ad8cc7 (7 commits) (flutter/engine#12361)
2019-09-19 skia-flutter-autoroll@skia.org Roll src/third_party/skia 18531cde2ab7..9a8b846baf43 (1 commits) (flutter/engine#12360)


If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC stuartmorgan@google.com on the revert to ensure that a human
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To report a problem with the AutoRoller itself, please file a bug:
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Documentation for the AutoRoller is here:
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Adds macOS support for `flutter create`:
- Currently it is behind a hidden flag.
- Adds a TargetPlatform workaround to lib/main.dart in the standard app template when enabled.
- Supports `app` and `plugin`; `module` support doesn't yet exist for macOS in general.

This will eliminate the need to use FDE's examples as templates on macOS. The templates are based on the current state of FDE's examples, with templating support added (and with adoption of the new application delegate in the app, which hadn't been done yet in FDE, eliminating some boilerplate from the template).

Fixes #30703 

Rather than have a monolithic .gitignore covering all platforms in the
app template, have each platform folder contain its own rules.

Fixes #40793

Started reading stored channel messages from ui.channelBuffers when handlers get set.

* Allow sending messages from the platform to the framework

* Add ability to send messages from the plugin to the platform.

Also adds [PluginEventChannel] which is the plugin counterpart to
EventChannel.

Fixes https://github.com/flutter/flutter/issues/39981

* fix analyzer errors

* Enhance doc comments

* Remove dead code in test

* Fixed Selectable text align is broken

1cada0a6d Roll src/third_party/skia 6344cbd1df76..18531cde2ab7 (2 commits) (flutter/engine#12358) (#40842)


git@github.com:flutter/engine.git/compare/bf3af4d157cc...1cada0a6dca6

git log bf3af4d157cc..1cada0a6dca6 --no-merges --oneline
2019-09-19 skia-flutter-autoroll@skia.org Roll src/third_party/skia 6344cbd1df76..18531cde2ab7 (2 commits) (flutter/engine#12358)


If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-engine-flutter-autoroll
Please CC stuartmorgan@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md