Roll Dart to version 7f9a9feae181573cca609fd1b8760d7992176699 (#6366)

* Roll Dart to version 7f9a9feae181573cca609fd1b8760d7992176699

This contains the following commits:

7f9a9feae1 [vm, service] Rename 'invoke' parameter 'receiverId' to 'targetId'.
fa3d8fa567 Don't check for the file presence in transitive sets when we are just creating it.
6f3de544ed [ VM / Hot Reload ] Fixed tests which were crashing periodically. Fixes issue #34599
e811b29788 [vm, gc] Restore growth policy when concurrent marking is not enabled.
0518b334ba Address comments
7c46a28505 Update convert class to mixin assist to remove "abstract"
06744c68b2 Pull reporting for unimplemented inherited members, and declared abstract members from ErrorVerifier.
45c7e4365c Update dartfix to apply changes to file rather than displaying them
9ad59bada2 [dartdevc] fix #34358, int to double conversion for literals
edddc0ba58 Generate source changes for converting class to mixin
2742a5d558 [Gardening] Update test status
d9de98e164 [VM] Delete some dead code in gen_snapshot.cc
51b8fc7bb0 AwaitExpression.precedence => 14
2390b3605f Create a package for shared diagnostics
629d76eb46 Simple dartfix that suggests class to be converted to mixins
8a2cfd8613 Implement InheritanceManager2.getMember() and use it in some places.
71eaf3209b Fix broken 'fasta testing sdk'.
d79f7493b3 Test that type parameters of typedefs are properly bounds checked.
b36f4fffc4 Allow multiple analyzer codes
82b3501c3c Fix supermixin handling in dart2js
c9b05d3f1f Allow super calls in mixin declarations
225b8d5075 Specialize Object properties in static type computation
4a58112a7c Move kernel_impact.dart from ssa/ to kernel/
aaf3b709e6 [release] Prepare changelog for 2.1.0-dev.6.0
e9c949372e Remove unused parts of J/K*Env classes
4659cb9480 Fully split JsToElementMap and KernelToElementMap
a617700b17 Removes code that has become redundant since 98a9adf.
7c54fab8a5 Adjust status files.
76470aca47 [VM] use coresnapshot when initializing an Isolate

* Address review comments.

DEPS

@@ -31,7 +31,7 @@ vars = {
   # Dart is: https://github.com/dart-lang/sdk/blob/master/DEPS.
   # You can use //tools/dart/create_updated_flutter_deps.py to produce
   # updated revision list of existing dependencies.
-  'dart_revision': '808ed6238b9262660e31ea826f7aea6cfa3a3493',
+  'dart_revision': '7f9a9feae181573cca609fd1b8760d7992176699',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py

ci/licenses_golden/licenses_third_party

-Signature: 298a107bb55f276ac38852045377a801
+Signature: 092b3d880fec4ee1110a9c0630e6da6a
 
 UNUSED LICENSES:
 

runtime/dart_isolate.cc

@@ -636,16 +636,6 @@ DartIsolate::CreateDartVMAndEmbedderObjectPair(
             (*raw_embedder_isolate)->child_isolate_preparer_));
   }
 
-  // TODO(rmacnak): This flag setting business preserves a side effect of using
-  // Dart_CreateIsolateFromKernel. It should be removed when some of the
-  // internal logic in reload no longer uses this flag.
-  Dart_IsolateFlags nonnull_flags;
-  if (flags == nullptr) {
-    Dart_IsolateFlagsInitialize(&nonnull_flags);
-    flags = &nonnull_flags;
-  }
-  flags->use_dart_frontend = true;
-
   // Create the Dart VM isolate and give it the embedder object as the baton.
   Dart_Isolate isolate = Dart_CreateIsolate(
       advisory_script_uri,         //