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)


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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)


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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)


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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)


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git@github.com:flutter/engine.git/compare/dd081bea0389...bf3af4d157cc

git log dd081bea0389..bf3af4d157cc --no-merges --oneline
2019-09-19 skia-flutter-autoroll@skia.org Roll src/third_party/skia e2a903e18b59..6344cbd1df76 (3 commits) (flutter/engine#12357)
2019-09-19 bkonyi@google.com Roll src/third_party/dart cb80ea7ba9..ea969c358e (52 commits)


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git@github.com:flutter/engine.git/compare/7fb14000fddf...dd081bea0389

git log 7fb14000fddf..dd081bea0389 --no-merges --oneline
2019-09-19 dnfield@google.com skip flaky test (flutter/engine#12355)


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git@github.com:flutter/engine.git/compare/92afbfdf544d...7fb14000fddf

git log 92afbfdf544d..7fb14000fddf --no-merges --oneline
2019-09-19 dnfield@google.com java lints (flutter/engine#12354)
2019-09-19 iska.kaushik@gmail.com [flutter_runner] Port vulkan surface changes (flutter/engine#12350)


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92afbfdf5 Roll src/third_party/skia f19f9caab2b4..e2a903e18b59 (1 commits) (flutter/engine#12351) (#40816)


git@github.com:flutter/engine.git/compare/eed16d34bd19...92afbfdf544d

git log eed16d34bd19..92afbfdf544d --no-merges --oneline
2019-09-19 skia-flutter-autoroll@skia.org Roll src/third_party/skia f19f9caab2b4..e2a903e18b59 (1 commits) (flutter/engine#12351)


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When the plugin list changes, iOS pods are invalidated, but that was
never wired up for macOS.

Should fix #39327

git@github.com:flutter/engine.git/compare/33ad6757e883...eed16d34bd19

git log 33ad6757e883..eed16d34bd19 --no-merges --oneline
2019-09-19 iska.kaushik@gmail.com [flutter_runner] Explicitly set |trace_skia| to false (flutter/engine#12349)
2019-09-19 iska.kaushik@gmail.com [flutter_runner] Port the new compilation trace from topaz (flutter/engine#12348)
2019-09-19 iska.kaushik@gmail.com [flutter_runner][async] Migrate dart/flutter to new async-loop APIs (flutter/engine#12347)
2019-09-19 iska.kaushik@gmail.com [flutter_runner] Move from runner context to component context (flutter/engine#12346)


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* Use separate isolate for image loading. Use TransferableTypedData to const-cost receive bytes from that isolate.

git@github.com:flutter/engine.git/compare/7f7250f47636...33ad6757e883

git log 7f7250f47636..33ad6757e883 --no-merges --oneline
2019-09-19 iska.kaushik@gmail.com [flutter_runner] Port over the tuning advice (flutter/engine#12345)
2019-09-19 iska.kaushik@gmail.com [flutter_runner] Remove usages of shared snapshots from CC sources (flutter/engine#12343)


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git@github.com:flutter/engine.git/compare/00a12c411f81...7f7250f47636

git log 00a12c411f81..7f7250f47636 --no-merges --oneline
2019-09-18 iska.kaushik@gmail.com [flutter_runner] Do not use prebuilts just yet (flutter/engine#12340)


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git@github.com:flutter/engine.git/compare/d3c60acef82c...00a12c411f81

git log d3c60acef82c..00a12c411f81 --no-merges --oneline
2019-09-18 dnfield@google.com Add missing CL, fix targets for Fuchsia (flutter/engine#12338)


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git@github.com:flutter/engine.git/compare/00f23b2e7356...d3c60acef82c

git log 00f23b2e7356..d3c60acef82c --no-merges --oneline
2019-09-18 ditman@gmail.com More controls for Screenshot tests (for web) (flutter/engine#12284)
2019-09-18 skia-flutter-autoroll@skia.org Roll src/third_party/skia 8391bac5c6f0..f19f9caab2b4 (8 commits) (flutter/engine#12341)


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* Simplified the serialization/deserialization logic of the Descendant/Ancestor matchers