Changes since last roll:
```
97674262bc [dart2js] Fix type argument with nnbd and extractTypeArguments.
ed2092e786 [vm] Add TFA transformer expectation files for unboxing metadata
44a4f366e2 [sdk] Updating Stream.contains to accept null values.
7e0139e0c0 [vm/corelib] Improve performance of list copying
ec8941b189 [dartdevc] Hoisting subtype caches to addTypeCaches.
f5a6554635 Move 'thisType' to ResolverVisitor.
b311a0052e Fixes REMOVE_UNUSED_FIELD and optional field formal parameters.
c83c9b40c5 [vm] Implement toString() for unboxing metadata, only write unboxing metadata if not fully boxed (which is default)
7ac22948e5 [CFE] More error for type variable in static contexts
30a12a349e Revert "Re-land "[vm] Aggressive write-barrier elimination.""
83378633e1 Add the attachment with the content of the file being analyzed.
bbb449dfa4 Issue 40931. Update inference constraint for T? to be non-nullable.
f1369d7896 Updated the invalid Example in num.dart
b22d3d6294 Add a P2 migration script for null safety migrator
db378a2f0d [ddc] let compiler generate instanceof and == of types directly.
617b78a014 [ddc] do not add null checks for parameters marked as @notNull
2ae10b14a3 [dart2js] Fix nullability of native methods.
b01cb58320 Revert "Re-land "[vm] Add type to _AsyncAwaitCompleter.start.""
043af430c1 Migraiton: Add function names to trace output.
005c5d7b52 Add an additional MMR "Max Rank 5" metric to the output of the completion_metrics.dart
52ad8dc2d2 Gather metrics on super invocations
f5dae48fac Add an ArgParser to completion_metrics.dart in the same manner as relevance_metrics.dart (https://dart-review.googlesource.com/c/sdk/+/138700)
a61e012e93 Migrate html tests using async_minitest and minitest
e3070b6f02 Add predicate to async_minitest
f8792406d8 Extract RemoveUnusedElement and RemoveUnusedField producers.
54e96f6ccf Add the `dynamic` keyword into additional missing portions of the AST (in method and constructor parameters) in the keyword_contributor.dart
8329bd7ca8 Do not check for '.analysis_options' for default options file in builder.
4f0fb8f9b0 Fix some syntax errors in the Dart code in the keyword_contributor_test.dart
4049ab54e4 Re-land "[vm] Add type to _AsyncAwaitCompleter.start."
8fb4645cae [dartdevc] Adding nnbd semantics for static and late fields.
fa2df01895 Null Safety preview: Fix description for uninitialized field
24c8021f03 Replace initialize() with declare().
9a62df57fa Fix a test to get the analyzer nnbd bot to pass
f17919b559 [nnbd/corelib] Fix performance regression in _SyncIterator.moveNext
6b71477d6e Add a host of server debugging options to dartdev migrate.
7617e327a1 [VM/Testing] - Turn on co19_2 legacy testing in NNBD bots.
4e79175ee8 Fix per-line highlighting in Null Safety preview tool
a4f6479998 [infra] Print details of unapproved (new or previous) failures in build failure message
eff1a9ff97 Re-land "[vm] Aggressive write-barrier elimination."
a629dbf073 Add a fix to inline a typedef
0f284647b1 [vm] Improve docs for Dart_LoadELF.
029c8f1cee [cfe] Use Supertype instead of InterfaceType in ClassHierarchyBuilder
e8c58a7a3d [CFE] Add ability to compare CompilerOptions
40507e7b13 [CFE] Tool for fasta -v statistics
7bdc910670 [infra] Remove unused bot script
7e815546ac Add the `dynamic` keyword into additional missing portions of the AST in the keyword_contributor.dart
7bc171483e Latest changes to the relevance metrics tool
3d0432eafc Add returnsNormally to async_minitest
6f47790fb6 [dartdevc] Optimize subtype check
4799f38767 [dartdevc] Optimize cast operation
c1cf29b2d4 [ddc] improve generated code for wrapType.isNormalized
6eae8db839 [ddc] remove dcall when accessing .type
de493465c8 Include 'dynamic' in the list of suggested keywords for type names, i.e. the 'dynamic' in "dynamic contents = ..."
80ed949678 [vm, reload] Don't drop unwind errors for isolates other than the first isolate in a group during a reload.
81c3208c10 [dart2js] Special case `null is T`.
de0fcd71d4 [dart2js] Assign the correct type to super tearoffs.
29d4b611fb Remove html_individual_config from indexeddb_1_test
9ba92779d6 Roll to latest package:watcher
8fd8fec185 [vm/aot] Add support to instance calls with unboxed parameters
2806ccacc7 [build] Update clang to 7e9747b50bcb1be28d4a3236571e8050835497a6.
972e045649 [analyzer] Fix windows paths again, and use ResourceProviderMixin.
e79f50098e Unify two error codes into one
2c5a56e7bb [vm] Disable late field init for constructor initialized fields
d3c0d59706 Disallow non-external generative JS constructors
60a81b0f51 Add hints to find equal elements in literal sets and maps
93ff9530aa Document difference between Stream.transform and Stream.map.
b0b8304b87 [Cleanup] Simplifies use_slow_path handling to remove unreachable asm.
b681bfd8d2 [VM] Fixes bad reuse/typing of temps in async transform invocations.
c1ed25dcf0 [CFE] Remove BulkCompiler
6facea722b [vm/ffi] Unbox Pointer data field - fix bytecode
7b6adc6083 Remove html_individual_config from remaining html tests
ce7fcff2ea Resolve type parameters to bounds when checking for implementing Iterable / Map.
a410f5bde1 [dart2js] rename null-safety flag and plumb through CFE
8ae984c54a [dart2js] Use a Symbol to access JavaScript Array Rti
a54a5eebb2 Remove html_individual_config from interactive_geolocation_test
69851f34c5 Remove the unused type hierarchy from the completion_metrics.dart
a2bf8dd351 Upgrade to dartdoc-0.30.2.
331067017f [vm] Fix late field store bug
9d76737487 Remove support for --emit-metadata in DDC
6e8efe2a15 Remove html_config from document_register_basic_test
a731b98113 [dart2js] Fix signature of identityHashCode.
3bab386570 Remove an unused shown name to remove a hint
ced0ceddd3 Rename an incorrectly named test class
739852d99d Migrate language_2/call to NNBD.
48c6180b46 [nnbd_migration] Hide hint insertion links after the migration is applied.
123a1ea517 [nnbd_migration] Fix 'apply edit' links.
3629658722 [nnbd_migration] Handle POST requests
5b0e439503 Fix windows path test/bots
5e66618175 Issue 40316. Verify only language version override locations at line starts.
110a29c9b3 Issue 40704. Support for ?[ in resolution.
55b4a240a4 [dart2js] Fix type promotion bug in static_type.dart.
a1992fec6d [ package:vm_service ] 4.0.0 release, Sentinels are now thrown, Future<dynamic> returns are now Future<Response>
bf5171cfd1 Add support for reporting how an accessed member related to the context type and extract feature computation
8d26e3df23 [vm] Don't insert CheckedSmi* instructions when the interface target suggests it's wrong.
f6b0a70230 Migrate language_2/await to NNBD.
1c64138e56 Migrate language_2/bool to NNBD.
1cf9d7a0c5 Revert "[vm] Add type to _AsyncAwaitCompleter.start."
2a8127dbfa [vm, gc] Take heap size into account when deciding when to start concurrent marking.
0649115b06 Rename VoidWithTypeParameters to VoidWithTypeArguments.
a74253987b Migration: add trace functionality to the preview tool.
d950783c07 [vm/ffi] Unify RawTypedData::data and Pointer::data
b406802981 [vm/ffi] Unbox Pointer data field
46bc5cd634 [vm] Support using different representations in ConvertUnboxedToUntagged
c135e2a7cd [vm/ffi] Reorder fields inside Pointer
4081235ac5 [vm] Support unboxed indices in indexed load and store
```
We believe this may be implicated in a Windows-specific crash during the
Flutter Gallery integration test.
See:
https://github.com/flutter/flutter/issues/51896
This reverts commit f9b78c5db2bc3087e1793947b11ca643c2d747cf.
