The Windows plugin CMake generation had code to ensure that the paths
written to it used POSIX separators, but the Linux version didn't; that
meant that plugin updates run on Windows machines would corrupt the
generated (but checked in) Linux CMake file.

This change shares that code so that both will use POSIX paths
regardless of what OS they are generated on.

Fixes https://github.com/flutter/flutter/issues/64591

* [flutter_tools] alternate the name of the dill file used for hot restart

* switch alternative name to .swap

Removes global variables and adds unit tests that can be copied for #65118

* 556cb237e Roll Skia from 6763a713f957 to d91cd6b5ee2b (3 revisions) (flutter/engine#20989)

* b6a3c5488 Roll Fuchsia Linux SDK from A0PKwETay... to gfAt63Ezd... (flutter/engine#21005)

* cceb7332e Roll Fuchsia Mac SDK from sih5f60Gt... to 9pfHLZEFU... (flutter/engine#21006)

* 5539820a6 Roll Skia from d91cd6b5ee2b to a73a84f9b8e3 (1 revision) (flutter/engine#21007)

* b4cc631cc Roll Dart SDK from f3a9ca88b664 to e59935669cb0 (1 revision) (flutter/engine#21008)

* 6cf0cc475 Roll Skia from a73a84f9b8e3 to d0fe7d37d678 (1 revision) (flutter/engine#21011)

* 5b055bbf5 Roll Skia from d0fe7d37d678 to 611a52108b01 (2 revisions) (flutter/engine#21012)

* 575a51948 Enable lazy-async-stacks by-default in all modes (Take 3) (flutter/engine#20895)

* 040a794b6 Roll Fuchsia Mac SDK from 9pfHLZEFU... to tUwahggJ8... (flutter/engine#21013)

* 22cca4cfd Roll Dart SDK from e59935669cb0 to f745f9447ddf (1 revision) (flutter/engine#21014)

* 539cb6985 Roll Fuchsia Linux SDK from gfAt63Ezd... to Ta3F40BV6... (flutter/engine#21015)

* 7d927dd4a Roll Dart SDK from f745f9447ddf to b88c06c314f4 (1 revision) (flutter/engine#21016)

* 09a5bf7ac Tweak the mdns error message (flutter/engine#20991)

* d0d9ce610 Roll Fuchsia Linux SDK from Ta3F40BV6... to coVjRTWSf... (flutter/engine#21018)

* 808bb859a Roll Fuchsia Mac SDK from tUwahggJ8... to TyNHQXzNU... (flutter/engine#21019)

* 5aa6921a5 Roll Skia from 611a52108b01 to cd54c8385c31 (2 revisions) (flutter/engine#21021)

* e7d558fbe Roll Dart SDK from b88c06c314f4 to 33b6c95936e0 (2 revisions) (flutter/engine#21023)

* af90dd366 Roll Skia from cd54c8385c31 to c0d3495e1ee2 (12 revisions) (flutter/engine#21024)

* f0fb74b8f Avoid crashing and display error if the process cannot be prepared for JIT mode Dart VM. (flutter/engine#20980)

* 6a6c23aaf Roll Skia from c0d3495e1ee2 to cf1a4f50121f (6 revisions) (flutter/engine#21026)

* 716dce086 Android 30r3 (flutter/engine#21025)

* 74310709f Roll Dart SDK from 33b6c95936e0 to a2c9cae4dcd8 (1 revision) (flutter/engine#21027)

* cef383d3f Roll Skia from cf1a4f50121f to 04b9443274cf (2 revisions) (flutter/engine#21028)

* cf8c6b8ba Update web lerpDouble to match C++ behaviour (flutter/engine#21010)

* 686667591 Roll Skia from 04b9443274cf to b8ae7fa12aa0 (1 revision) (flutter/engine#21030)

* c538f40d3 Roll Dart SDK from a2c9cae4dcd8 to ffbfa2000435 (1 revision) (flutter/engine#21031)

* 89d34b0f3 Roll Skia from b8ae7fa12aa0 to 445c8ebcb710 (1 revision) (flutter/engine#21032)

* 7766d2e2b Roll Fuchsia Mac SDK from TyNHQXzNU... to Phn3nF_BJ... (flutter/engine#21034)

* e3de8d0f1 Roll Fuchsia Linux SDK from coVjRTWSf... to eBus_y4DN... (flutter/engine#21035)

* beb7df506 Roll Skia from 445c8ebcb710 to f9d5940fef55 (3 revisions) (flutter/engine#21037)

* f3a17b63d Roll Skia from f9d5940fef55 to 81c6d6eeb4cf (1 revision) (flutter/engine#21038)

* bbcc495b1 Roll Dart SDK from ffbfa2000435 to 2e838b7b4503 (2 revisions) (flutter/engine#21039)

* 61062fdbc Roll Skia from 81c6d6eeb4cf to 81606b5d9774 (5 revisions) (flutter/engine#21041)

* f7c7b41f0 Revert "Enable lazy-async-stacks by-default in all modes (Take 3) (#20895)" (flutter/engine#21043)

This reverts commit e682ec71.

This is in preparation to enable the new mac builders.

Bug:
  https://github.com/flutter/flutter/issues/65223

* migrate widget to nullsafety

* remove double blank line after license

* address review comments in actions.dart

* nullable ObjectKey.value

* use local variable oldElement

* make State.build non-nullable

* make State.context non-nullable

* newline at eof

* make ProxyWidget.child non-nullable

* make _InactiveElements.debugContains non-nullable

* make Element.depth non-nullable

* make ProxyElement.build non-nullable

* make StatefulElement.state non-nullable

* remove 'Notice that'

* avoid cast of list in RenderObjectElement.updateChildren

* make IndexedSlot.value non-nullable

* avoid cast of list in MultiChildRenderObjectElement.mount

* make some WidgetsApp parameters non-nullable

* hitTest take non-nullable position

* make ScrollableState.position non-nullable

* use _pixels instead of pixels

* make ViewportOffset.pixels non-nullable

* make param and return type of IndexedWidgetBuilder non-nullable

* unused_import

* make context param non-nullable for Builder in animated_list.dart

* make ScrollMetrics.viewportDimension non-nullable

* make ScrollMetrics.{min,max}ScrollExtent non-nullable

* make _Location.file non-nullable

* _WidgetForTypeTests.createElement throw UnimplementedError

* update _NullWidget.build error message

* make _ShortcutsState.manager non-nullable

* Fix childCount issues for NNBD

* fix childCount computation on web

* increase max value on js side to compute childCount

* make aspect parameter of dependOnInheritedWidgetOfExactType nullable

* merge has{min,max}ScrollExtent into hasScrollExtents

* update focus_manager.dart

* address review comments in icon.dart

* address review comments in image.dart

* address review comments in routes.dart

* address review comments in scroll_activity.dart

* update doc comments

* make UserScrollNotification.direction non-nullable and required

* rename hasScrollExtents to hasContentDimensions

* unnecessary late
Co-authored-by: Ian Hickson <ian@hixie.ch>

I modified TextAlign docs because the descriptions of TextAlign.center and Center Widget are so similar that they cause confusion.

Fixes https://github.com/flutter/flutter/issues/5805

Integration tests must only go through the real file system/process manager/platform. The global indirection makes this code harder to understand than if it directly referred to the concrete instances that are being used.

Update the integration shard to use a const instance of a LocalFIleSystem, LocalProcessManager, and LocalPlatform. Remove global usage and apply testWithoutContext.

Currently the framework uses fairly large "hit slop" values to disambiguate taps from drags/pans. This makes sense on touch devices where the interaction is not very precise, on mice however it can feel as if the UI is lagging. This is immediately noticeable on our infra dashboard, where it takes almost half of a grid square of drag before the actual drag kicks in.

One potential solution is to always use smaller constants depending on whether the interaction is mouse or touch based. The only reasonable choice is to use the pointer device kind and not target platform - same platform can have different input sources. This requires exposing the pointer device kind in a few new places in several of the gesture detectors, and using the enum to compute the correct hit slop from an expanded set of constants.

This almost works, however there are a few places (notably ListViews) which uses the touch hit slop as a default value in scroll physics. It does not seem like it will be easy to disambiguate a user provided scroll physics constant from the default and/or adjust it somehow - this might require significant changes to scroll physics which I have left out of this PR.

This PR does not adjust:

kTouchSlop used in scroll_physics.dart's minFlingDistance
kTouchSlop used in PrimaryPointerGestureRecognizer/LongPressGestureRecognizer

Allow Developers to enable Accessibility testing on WebFlutterDriver and get the underlying webDriver (#65051)

This allows us to rationalize the nullability of some of our APIs.
Prior to this we'd end up in a situation where Container assumed that
getClipPath would be non-null but Decoration was ok with return null.

* 30b829e7e Populates fuchsia node actions in semantics updates. (flutter/engine#20451)

* c2e70109f Roll Skia from 1ee21cdfb6fe to 6763a713f957 (1 revision) (flutter/engine#20982)

* 841401db8 restore FML_DCHECK removed due to a code reviewing error (flutter/engine#20953)

* 367c6dbd1 Don't use GetTaskQueueId() in rasterizer as it breaks Fuchsia (flutter/engine#20983)

* b22a8c69d Let FlutterActivity/Fragment/FragmentActivity have an app bundle path override instead of eager resolving during construction (flutter/engine#20769)

* 0f0ae681e Update test Dart code to pass the latest Dart analyzer rules (flutter/engine#20986)

* d77dd3101 Manual roll of Dart b29f228f62...016e8880f0 (flutter/engine#20967)

* c7b3d5304 Roll Fuchsia Mac SDK from gOI3W1UNU... to EN2ycWLxi... (flutter/engine#20985)

* 6a6986da4 improve sensitivity of BackdropFilter web tests (flutter/engine#20915)

* 9fc9cb2b9 Roll Dart SDK from 016e8880f0ab to 0f0cff3922ad (7 revisions) (flutter/engine#20990)

* 242d52207 [Android R] Sync keyboard animation with view insets vs Android 11/R/API 30 WindowInsetsAnimation (flutter/engine#20843)

* b4e089639 Roll Fuchsia Linux SDK from 81O8Kg_Rw... to A0PKwETay... (flutter/engine#20998)

* d77c4e540 adjust blur radius for HTML to match CanvasKit (flutter/engine#20840)

* 0628492e7 Roll Dart SDK from 0f0cff3922ad to f3a9ca88b664 (1 revision) (flutter/engine#21000)

* d1d848e84 Roll Fuchsia Mac SDK from EN2ycWLxi... to sih5f60Gt... (flutter/engine#20999)

This reverts commit cb4b8677.

This reverts commit db4dda20.

This reverts commit 48f1a0a8.

Similar to the permission denied error on Windows, this is not resolvable by the tool.

* 5e54c707e Reland: Enable hybrid composition by default on Android (#20722) (flutter/engine#20864)

* 939871799 Roll Skia from db5582b71116 to 44e96bee4b6a (4 revisions) (flutter/engine#20908)

* 5f49a9549 Add auto plugin registration to FlutterFragmentActivity as well (flutter/engine#20865)

* c4c4f341b Wait for first frame before checking layer tree (flutter/engine#20910)

* 0773bf0bd Roll Skia from 44e96bee4b6a to 3913d3e137ed (2 revisions) (flutter/engine#20909)

* 8ec8af75a [windows] Add horizontal scroll support (flutter/engine#20668)

* 1bd9b8e85 Reset Shell::weak_factory_gpu_ on the raster thread (flutter/engine#20869)

* d67923feb Pass text input key events to the EventResponder if they do not yield characters (flutter/engine#20912)

* abe10d102 Roll Dart SDK from 84c3eacc7ba0 to 6eab35f49cbb (2 revisions) (flutter/engine#20913)

* 101316b76 [web] migrate from e2e to integration_test (flutter/engine#20914)

* 1f52ec378 Roll Dart SDK from 6eab35f49cbb to 2a5f37d25453 (1 revision) (flutter/engine#20917)

* 80190580d Default C++ wrapper templates to EncodableValue (flutter/engine#20760)

* 5f3ec38c2 Roll Fuchsia Mac SDK from sI2DAAmSI... to waj2pOhDh... (flutter/engine#20919)

* a65102097 Roll Fuchsia Linux SDK from _SVZn8uN2... to 9tLNFbjA1... (flutter/engine#20920)

* 696c2aafe Roll Skia from 3913d3e137ed to 7b46300fe4ff (4 revisions) (flutter/engine#20924)

* 95f2b7272 Create root isolate asynchronously (flutter/engine#20142)

* 58a620765 Adds fuchsia node roles to accessibility bridge updates. (flutter/engine#20385)

* a76214307 Roll Dart SDK from 2a5f37d25453 to e8e0d5a539fb (3 revisions) (flutter/engine#20928)

* 49d680532 Ensure all images are closed in FlutterImageView (flutter/engine#20842)

* d67bda725 Image.toByteData and Picture.toImage implementations (#3) (flutter/engine#20750)

* 96efe3927 Revert "Adds fuchsia node roles to accessibility bridge updates. (#20385)" (flutter/engine#20936)

* 5585ed990 Revert "Create root isolate asynchronously (#20142)" (flutter/engine#20937)

* f6270c041 Roll Dart SDK from e8e0d5a539fb to b29f228f62e2 (3 revisions) (flutter/engine#20939)

* 15bf1bbf6 [Android R] Integrate DisplayCutouts into viewportMetrics (flutter/engine#20921)

* 615e66801 Clear the GL context only after submitting the frame (flutter/engine#20931)

* ca989b8ae Roll Skia from 7b46300fe4ff to 1338a37a1add (16 revisions) (flutter/engine#20943)

* 8f3f71145 Roll Fuchsia Linux SDK from 9tLNFbjA1... to knpSoAoZq... (flutter/engine#20944)

* 873c00793 Log exception in addition to the stack trace for unhandled exceptions. (flutter/engine#20935)

* d761629cb Roll Skia from 1338a37a1add to 8fa3b4e8cde5 (6 revisions) (flutter/engine#20949)

* f6920dae5 Roll Skia from 8fa3b4e8cde5 to e9a9ad908226 (5 revisions) (flutter/engine#20952)

* 634e499bc Use hint freed specifically for image disposal (flutter/engine#20754)

* c700479db Revert external size changes to Picture (flutter/engine#20950)

* 435379757 Roll Skia from e9a9ad908226 to 3d1d636cd839 (6 revisions) (flutter/engine#20955)

* 80f4481d2 renaming e2e tests to integration (flutter/engine#20954)

* 61e057aa5 Clear GL context before Gr context (flutter/engine#20957)

* f43c3d766 Roll Fuchsia Mac SDK from waj2pOhDh... to 0r88gDzUP... (flutter/engine#20958)

* 5a2db338e Roll Skia from 3d1d636cd839 to 683beccf6776 (13 revisions) (flutter/engine#20961)

* efb339f30 Only clear GL context after changing the thread configuration (flutter/engine#20965)

* 58d5132e0 Roll Fuchsia Linux SDK from knpSoAoZq... to odFvFQV9Z... (flutter/engine#20968)

* 3729fdb79 Roll Skia from 683beccf6776 to a66a9c31a318 (4 revisions) (flutter/engine#20969)

* 40fe7f359 Roll Fuchsia Mac SDK from 0r88gDzUP... to gOI3W1UNU... (flutter/engine#20970)

* e979c29a2 Roll Skia from a66a9c31a318 to be72801f29f9 (1 revision) (flutter/engine#20971)

* 6e8930b26 Roll Skia from be72801f29f9 to f8823b572600 (1 revision) (flutter/engine#20973)

* 68b7b8401 [fuchsia] Send trace events to system tracing on all configurations (flutter/engine#20974)

* 3f05b521b Always set the callback during Rasterizer setup (flutter/engine#20976)