Add document for mouse cursor mapping on Windows and Linux.

* migrate foundation to nullsafety

* address review comments

Enable null safety asserts for web debug mode. This induces runtime asserts at the boundaries between null safe and non-null safe libraries. Adds integration test that validates assertion error is thrown.

#61042

Revert "Reland "Add support for Dart Development Service (DDS) in Flutter Tools (#61276)" (#61395)" (#61498)

This reverts commit f98184e4.

This reverts commit 5b9c6e2b.

This reverts commit 9f4499f4.

For #61407 , we need to be able to find all widgets that of a given type. Previously I experimented with using the type name, but of course this does not handles subtypes. The actual check needs to be an is check.

Since there is no way to convert a String to a Type at runtime for use in this check, we can instead evaluate an expression which assigns a closure to a field. The idea for this was inspired by how the dart devtools adds debug functionality to older versions of flutter.

Since the reload feature is not complete yet, adds an integration test which simulates how it will eventually behave

Implements the flutter config feature for #61407 , but does not implement any of the functionality.

* Improve error reporting for RenderObject visitChildren errors

* Nits and fixes

Updates the activity indicator style to iOS14, but places it behind a flag, to be deprecated when iOS 14 is released.

* 160b268ef Set locale in Linux shell (flutter/engine#19470)

* c479b9370 Fix documentation of unset platform view ID (flutter/engine#19320)

* f3ab78dc1 Fix clipboard paste functionality not working (flutter/engine#19489)

* 934534758 Added the ability to set properties in interface builder for FlutterViewController. (flutter/engine#19458)

* 69fdf6d1b Use identical in hashValues instead of operator== (flutter/engine#19615)

* 3dc81635d [android] Pass synthesized eventType to VirtualDisplay platform views and fix memory leak (flutter/engine#19620)

* b16c47d57 using text capitalization value in web (flutter/engine#19564)

* 49c0161ff Roll Skia from 16bf7d31c819 to 4d48bb35972f (32 revisions) (flutter/engine#19635)

* 2d6afa7fa Roll Skia from 4d48bb35972f to 9f821489c9f3 (4 revisions) (flutter/engine#19638)

* 35f59b922 Roll Fuchsia Linux SDK from NC9pp... to 5R9a0... (flutter/engine#19639)

* 53038e298 Roll Fuchsia Mac SDK from iwQCA... to Wym-S... (flutter/engine#19640)

* d9e68f420 Roll Skia from 9f821489c9f3 to f8a6b5b4b0d0 (1 revision) (flutter/engine#19643)

* d32961748 Changes to fix build errors in google3. (flutter/engine#19616)

* dd0a6c403 Roll Skia from f8a6b5b4b0d0 to 5160e8caa226 (9 revisions) (flutter/engine#19647)

* d98d539cb Manual Roll of Dart dfdc7e45c5...06cb010247 (flutter/engine#19649)

* dfd072715 don't throw error for the new autofill request (flutter/engine#19633)

* 39e98d28b Manual Skia roll to c91db040ad18b9cc3236e342e9acca020eaafd10 (flutter/engine#19650)

* f9acd080b Avoid a copy in EncodeImage (flutter/engine#19504)

* 7e101f1ee Roll Fuchsia Linux SDK from 5R9a0... to GOf1K... (flutter/engine#19656)

* f3be9f1bc Incorporate compat info changes into flutter engine (flutter/engine#19606)

* 9188ff66c Manual Roll of Dart 707c6404f9...dfdc7e45c5 (flutter/engine#19657)

* cbdd3e2d4 Roll Fuchsia Mac SDK from Wym-S... to -v4bL... (flutter/engine#19661)

* 6efb152dc Roll Dart SDK from 707c6404f969 to 0e25306d3f78 (4 revisions) (flutter/engine#19666)

* 22a440c67 Roll Dart SDK from 0e25306d3f78 to 6d06476bae6b (1 revision) (flutter/engine#19669)

* 806392328 Roll Fuchsia Linux SDK from GOf1K... to QWI76... (flutter/engine#19671)

* c99deb009 CkPaint uses SkPaint (flutter/engine#19562)

* 015f2ea76 Use the main bundle if the App bundle is not found (flutter/engine#18749)

* f82d30b7c Roll Dart SDK from 6d06476bae6b to a9e67d81941a (3 revisions) (flutter/engine#19677)

* 61b2fd2e3 Roll Fuchsia Mac SDK from -v4bL... to phQJt... (flutter/engine#19681)

* 74b541da2 Roll Fuchsia Linux SDK from QWI76... to mrlGt... (flutter/engine#19682)

* 25ce3db77 Roll Skia from c91db040ad18 to e4f36d7ac8f5 (20 revisions) (flutter/engine#19686)

* 162dba1ab Roll Skia from e4f36d7ac8f5 to ed15b1c39b8b (1 revision) (flutter/engine#19687)

* f97c38b01 Roll Fuchsia Mac SDK from phQJt... to kEVc6... (flutter/engine#19688)

* 40c4ee845 Roll Fuchsia Linux SDK from mrlGt... to YfVT0... (flutter/engine#19690)

* ec944b0f1 Roll Skia from ed15b1c39b8b to 1434ce1aa94d (1 revision) (flutter/engine#19692)

* 7ce988acf Roll Skia from 1434ce1aa94d to f64be13cbf84 (2 revisions) (flutter/engine#19695)

* 5f7ca41a5 Roll Fuchsia Mac SDK from kEVc6... to hRul_... (flutter/engine#19696)

* d24549cfe Roll Skia from f64be13cbf84 to 041796e60364 (3 revisions) (flutter/engine#19697)

* 617bd8866 Roll Dart SDK from a9e67d81941a to fecc8163afc7 (3 revisions) (flutter/engine#19703)

* 8d241e492 [Android] Prevent FlutterRenderer listener from calling JNI after detach (flutter/engine#19558)

* 309e514dd Roll Skia from 041796e60364 to d1ce4cb2beb8 (2 revisions) (flutter/engine#19704)

* 211f18edb Roll Skia from d1ce4cb2beb8 to 7c1967700b44 (6 revisions) (flutter/engine#19707)

* 0532227fc Roll Skia from 7c1967700b44 to 439709a97dfd (8 revisions) (flutter/engine#19712)

* 1e02bfd6a Support decimal information on the TextInputType (flutter/engine#19664)

* 7a95e32fc Linux: Use a hash table to map cursors (flutter/engine#19561)

* df2304489 [web] Implement ulps for path ops (flutter/engine#19711)

* 4a3aa4dc8 Fixes typo in android_context_gl.h (flutter/engine#19700)

* 5b966eb3f Roll Skia from 439709a97dfd to 2604a89d3353 (3 revisions) (flutter/engine#19715)

* d024ae400 [fuchsia] Use memory_requirements_2 extension. (flutter/engine#19678)

* 4392fbf8f Roll Fuchsia Linux SDK from YfVT0... to 2ct5j... (flutter/engine#19720)

* ab05c7959 Roll Fuchsia Mac SDK from hRul_... to ZXLvD... (flutter/engine#19721)

* c05ca7e7f Roll Dart SDK from fecc8163afc7 to f997d62a6d29 (13 revisions) (flutter/engine#19722)

* ae3797121 Remove xcpretty from unit tests to see full output on test failures (flutter/engine#19667)

* 91f80efd3 Moved to RMSE for image comparison to account for slight variations in golden image tests (flutter/engine#19658)

* 1e23309a3 Wait for platform view to appear in iOS UI tests (flutter/engine#19725)