Added mainAxisExtent to SliverGridDelegateWithFixedCrossAxisCount and SliverGridDelegateWithMaxCrossAxisExtent (#71376)

* 52ec2ddd8 Roll Fuchsia Linux SDK from _l04etgVd... to nkgnDjAl3... (flutter/engine#23170)

* f32ec0cd6 Roll Fuchsia Mac SDK from RDUxjnng0... to QDs-PyheO... (flutter/engine#23177)

* 7983c6fda Roll Dart SDK from b59de86059f3 to 2a78a2978983 (1 revision) (flutter/engine#23179)

* c608b07da bump fuchsia toolchain to clang-12 (flutter/engine#23067)

* 8a3e9a2b9 fix crash in FontCollection::init() when FontFamily is empty (flutter/engine#23019)

* 95ba5ca89 Roll Skia from 6f31e27f1e29 to 85fa75616dfe (7 revisions) (flutter/engine#23118)

* 50e7d8916 [web] Switch web-render option default to auto (flutter/engine#23090)

* 885452086 Roll Skia from 85fa75616dfe to d6f2338ab194 (3 revisions) (flutter/engine#23119)

* acad21c19 [web] Tests for rich paragraph DOM (flutter/engine#23097)

* 27ebbc4bf Rename PointerState.isDown as per style guide (flutter/engine#23120)

* 19950f576 [web] Rich paragraph getBoxesForRange (flutter/engine#23098)

* 581acbe98 Roll Skia from d6f2338ab194 to 1d89532d5988 (1 revision) (flutter/engine#23122)

* 540b1918e Roll Fuchsia Mac SDK from acylwa3i4... to chLTYsKMR... (flutter/engine#23125)

* 3b52edff6 Roll Skia from 1d89532d5988 to 7839f66540b6 (1 revision) (flutter/engine#23126)

* 6b25350af Roll Fuchsia Linux SDK from TIKHoiQyP... to wu6yV-_BL... (flutter/engine#23127)

* 9c72085b7 Roll Skia from 7839f66540b6 to 20f1b3462878 (1 revision) (flutter/engine#23129)

* ee323d0f0 Roll Skia from 20f1b3462878 to 995f0366bd21 (2 revisions) (flutter/engine#23132)

* 625aa695e Roll Skia from 995f0366bd21 to b64da3907f76 (1 revision) (flutter/engine#23135)

* affc4216f Roll Skia from b64da3907f76 to 81da68af2ecf (7 revisions) (flutter/engine#23142)

* 9a6a31e00 Roll Fuchsia Mac SDK from chLTYsKMR... to RDUxjnng0... (flutter/engine#23143)

* 78657edbb Added golden test to make sure that spawn engines work. (flutter/engine#23066)

* bb9cac29a Roll Fuchsia Linux SDK from wu6yV-_BL... to _l04etgVd... (flutter/engine#23145)

* 51c9ae956 Add --strict_null_safety_checks to the Dart flag allowlist (flutter/engine#23144)

* 76310c426 Add missing sdk constriant in pubspec.yaml files. (flutter/engine#23124)

* 6e54f0d2d [fuchsia] Add wrapper for zx_clock_get_monotonic. (flutter/engine#23128)

* ade75e08f [web] Rich paragraph getPositionForOffset (flutter/engine#23133)

* 2ef2c8616 Fix engine in preparation for implementing https://github.com/dart-lang/language/issues/1274 (flutter/engine#23131)

* 9384324cc Update android_lint deps (flutter/engine#23151)

* ea4bb2ae4 Roll Skia from 81da68af2ecf to 7b920446a8fc (14 revisions) (flutter/engine#23152)

* 4b5e4e605 Make it easier to turn on Xcode symlinks (flutter/engine#23150)

* 325f06958 Roll fuchsia toolchain (flutter/engine#23155)

* 05704d312 Use include for C/C++ headers in darwin/macos (flutter/engine#23035)

* 8d3d69b6b Turned no malloc scribble and randomized the tests. (flutter/engine#23014)

* 418cc488e Fix macOS crash when modifier keys pressed. (flutter/engine#23154)

* a8c360dc2 Update FlutterPlatformViewsTests (flutter/engine#23158)

* d941aefa6 [web] Rich text painting on bitmap canvas (flutter/engine#23136)

* 67cb0f382 Revert "[web] Switch web-render option default to auto (#23090)" (flutter/engine#23161)

* c4b48c554 Roll Skia from 7b920446a8fc to dfc880bd9ba0 (14 revisions) (flutter/engine#23164)

* de1de9d44 Disable FlutterPluginAppLifeCycleDelegateTest testWillResignActive (flutter/engine#23166)

Fixes https://github.com/flutter/flutter/issues/71972

* remove flaky flag

* remove from manifest

* fix test

selectionEnabled was not taken into account in:

key movement handling in RenderEditable
mouse drag handling in TextSelectionGestureDetectorBuilder

Add a check that a pubspec file exists before trying to read it.