* Change assert_bundle_package_font_test to memory file system

This is to work towards being able to run the tests without `-j1` (#21113). These tests were using the real filesystem and setting/relying on fs.currentDirectory. There was a comment about this being because the memory provider didnt' support POSIX and Windows, however that seems to have changed since (and many other asset tests already do something similar to this).

* Trim trailing whitespace

* Add a workaround for Windows path slash directions

Strictly this is correct, but the real FS can tolerate either path. The in-memory file system is more strict (see https://github.com/google/file.dart/issues/112).

* Extract a helper for writing schema files in tests

* Missed file when saving!

* Remove redundant comment

* Rename writeBasicSchema -> writeEmptySchema

* Use the file we already have to write contents

* Make comments more descriptive

* Remove another dupe of writeSchema to use the shared one

* Rename schema -> pubspec_schema

* Trim whitespace

This patch eliminates the --preview-dart-2/--no-preview-dart-2 flag,
hardcoding all uses to true. It also defaults all previewDart2 method
parameters to true, where they hadn't yet been.

A series of subsequent patches will eliminate all previewDart2
parameters and the associated code from within the codebase.

* Unskip integration tests on Windows that now pass

The referenced issue is closed and these tests pass for me locally on Windows now.

* Remove import that's no longer used

* Add another issue that is afffecting these tests on Windows

* Add a hot restart test and mark skip on Windows

Skipped due to https://github.com/flutter/flutter/issues/21348.

https://github.com/flutter/engine/compare/77fad1a731f2...de4c7a53f21c

git log 77fad1a731f2..de4c7a53f21c --no-merges --oneline
de4c7a53f Roll src/third_party/skia 09a7bb222172..88119de2b849 (1 commits) (flutter/engine#6146)


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https://github.com/flutter/engine/compare/2318a5274af4...77fad1a731f2

git log 2318a5274af4..77fad1a731f2 --no-merges --oneline
77fad1a73 Roll src/third_party/skia 2f53025e8bf1..09a7bb222172 (1 commits) (flutter/engine#6144)


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https://github.com/flutter/engine/compare/d88e0b8229ec...2318a5274af4

git log d88e0b8229ec..2318a5274af4 --no-merges --oneline
2318a5274 Roll src/third_party/skia ca858b68c34b..2f53025e8bf1 (1 commits) (flutter/engine#6143)


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https://github.com/flutter/engine/compare/949fb0fb4cbe...d88e0b8229ec

git log 949fb0fb4cbe..d88e0b8229ec --no-merges --oneline
d88e0b822 Roll src/third_party/skia 2f8c60e28682..ca858b68c34b (2 commits) (flutter/engine#6142)


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https://github.com/flutter/engine/compare/a4471589f2cd...949fb0fb4cbe

git log a4471589f2cd..949fb0fb4cbe --no-merges --oneline
949fb0fb4 Roll src/third_party/skia 8534723c7be1..2f8c60e28682 (1 commits) (flutter/engine#6141)


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https://github.com/flutter/engine/compare/017dafd42660...a4471589f2cd

git log 017dafd42660..a4471589f2cd --no-merges --oneline
a4471589f Roll src/third_party/skia e8e12e89c46b..8534723c7be1 (1 commits) (flutter/engine#6140)
db3484f27 Fix crash in text layout when GetMinikinFontCollectionForStyle returns null. (flutter/engine#6139)
0f7bfeaf4 Roll src/third_party/skia 6487e5ca6f10..e8e12e89c46b (1 commits) (flutter/engine#6138)
f25d89a2d Fix windows embedder builds. (flutter/engine#6137)
b3c778fe9 Allow embedders to specify software renderer configs. (flutter/engine#6133)
da419912d Roll src/third_party/skia 7bfe8438a94b..6487e5ca6f10 (6 commits) (flutter/engine#6136)
f44c0008b Roll src/third_party/skia 62db8d577931..7bfe8438a94b (20 commits) (flutter/engine#6134)
fbf672643 Mark deprecated Flutter iOS APIs as unavailable (flutter/engine#6124)


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This was a bug, when e.g a LongPressGestureRecognizer was in the gesture
arena, the android view gesture team may not yet win the arena when the
last pointer was up. This change allows AndroidView to win the gesture
even after all pointers are up.

https://github.com/flutter/engine/compare/f612a761c2f0...017dafd42660

git log f612a761c2f0..017dafd42660 --no-merges --oneline
017dafd42 Roll buildroot to 35959f6255c341eee550884ed69afd6b2891bd53 (unbreaks Windows) (flutter/engine#6132)
842546824 Roll buildroot to pick up new NDK r17b (flutter/engine#6131)


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DevFS.update only runs in Dart 2 mode when the generator parameter is
supplied. In Dart 2 mode, both mainPath and pathToReload are required
parameters; this patch marks them as such.

generator is required for running in Dart 2. All call sites other than tests already explicitly set this value.

Note the statements on line 510 and line 516 for why mainPath and pathToReload are required.

Its type uses a generic type which is limited to library-visibility.
Eliminating compilationQueue from ResidentCompiler's public interface
makes it possible to mock in tests.

https://github.com/flutter/engine/compare/90faf8531c00...f612a761c2f0

git log 90faf8531c00..f612a761c2f0 --no-merges --oneline
f612a761c Roll src/third_party/skia 8ff2f13f3817..62db8d577931 (21 commits) (flutter/engine#6130)


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https://github.com/flutter/engine/compare/a114659c4a83...90faf8531c00

git log a114659c4a83..90faf8531c00 --no-merges --oneline
90faf8531 Roll src/third_party/skia f8592a69428e..8ff2f13f3817 (1 commits) (flutter/engine#6129)


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https://github.com/flutter/engine/compare/dc7b5eb89da3...a114659c4a83

git log dc7b5eb89da3..a114659c4a83 --no-merges --oneline
a114659c4 Roll src/third_party/skia 381efe73499e..f8592a69428e (1 commits) (flutter/engine#6127)
21ac961df Roll src/third_party/skia 8e318fda76df..381efe73499e (11 commits) (flutter/engine#6126)
e7767ae9b Add license file patching instructions to README (flutter/engine#6125)
51d4be774 Add a `-[FlutterViewController splashScreenView]` property (flutter/engine#6112)
a047fd20f Roll src/third_party/skia 7ed0eae0cd13..8e318fda76df (17 commits) (flutter/engine#6123)


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This fixes https://github.com/flutter/flutter/issues/20746

https://github.com/flutter/flutter/issues/19578

Flutter commands all default to --preview-dart-2. Eliminate support for
the use of this option and the previewDart2 parameter in dev/devicelab
tests.

Normalize file path to non-Windows so string path comparison works.

Clarify the intent of these tests.

https://github.com/flutter/engine/compare/252da4808277...dc7b5eb89da3

git log 252da4808277..dc7b5eb89da3 --no-merges --oneline
dc7b5eb89 Use Skia normalize again after Skia precision fix. (flutter/engine#6121)
1c7682418 entering a character with a selection deletes the selection (flutter/engine#6113)
9fc355d2c Roll src/third_party/skia cd7907b57d76..7ed0eae0cd13 (1 commits) (flutter/engine#6120)
6586016da Roll src/third_party/skia f7c723c93d26..cd7907b57d76 (1 commits) (flutter/engine#6119)
1fa5fe6a0 Roll src/third_party/skia eb0bb732f43f..f7c723c93d26 (3 commits) (flutter/engine#6118)


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* Pass uri instead of filepaths when hot-reloading.

Bug: https://github.com/flutter/flutter/issues/21168

* Remove imports. Enable another test

* Restore skipping of test on mac

This adds links to the already existing animated diagrams in the asset-for-api-docs repo.