Roll src/third_party/dart 862d5012ae9c..515d4bd7adb1 (18 commits) (#15683)

https://dart.googlesource.com/sdk.git/+log/862d5012ae9c..515d4bd7adb1

git log 862d5012ae9c..515d4bd7adb1 --date=short --first-parent --format='%ad %ae %s'
2020-01-15 markzipan@google.com [dartdevc] Emitting equality checks that disregard 'legacy' wrappers for type objects.
2020-01-15 jwren@google.com In completion_metrics.dart, print out line numbers instead of character offsets.
2020-01-15 scheglov@google.com Fix for crash: type 'DefaultParameterElementImpl' is not a subtype of type 'FieldFormalParameterElementImpl'
2020-01-15 jwren@google.com Improve printPercentage(..) in pkg/analysis_server/lib/src/status/pages.dart to take an optional fractionDigits to pass to num.toStringAsFixed(..)
2020-01-15 mfairhurst@google.com [nnbd_migration] Mark implicit dynamic for type params as nullable
2020-01-15 scheglov@google.com Report LATE_FINAL_LOCAL_ALREADY_ASSIGNED.
2020-01-15 jwren@google.com Rename a class in pkg/analysis_server/tool/completion_metrics/completion_metrics.dart
2020-01-15 jwren@google.com Improve the print output from the completion_metrics.dart tool, output for collection is now: Summary for /usr/local/google/home/jwren/github/collection: Total number of completion tests   = 11487 Number of successful completions   = 9945 (86.6%) Number of unsuccessful completions = 1542 (13.4%)
2020-01-15 jwren@google.com Implement the rest of the visit* methods in pkg/analysis_server/tool/completion_metrics/visitors.dart, members sorted.
2020-01-15 nshahan@google.com [dart:async] Fix error in NNBD fork
2020-01-15 asiva@google.com [VM/isolate] Migrate 'dart:isolate' and patch files for NNBD
2020-01-15 pquitslund@google.com linter bump to 0.1.109
2020-01-15 whesse@google.com [infra] Use analyzer-unittest-asserts and cfe-unittest-asserts configurations
2020-01-15 johnniwinther@google.com [cfe] Avoid crash on late field override
2020-01-15 paulberry@google.com Migration: small simplification to _PassThroughBuilderImpl.
2020-01-15 paulberry@google.com Migration: test removal of all list elements when there is a trailing separator
2020-01-15 johnniwinther@google.com [cfe] Add opt-out version of general testcases
2020-01-15 dmitryas@google.com [cfe] Use nullable context on LHS of if-null expressions

Created with:
  gclient setdep -r src/third_party/dart@515d4bd7adb1

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/dart-sdk-flutter-engine
Please CC dart-vm-team@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

Bug: None
Tbr: dart-vm-team@google.com

DEPS

@@ -34,7 +34,7 @@ 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': '862d5012ae9ceb43282ec23034e8031d06f8a1f9',
+  'dart_revision': '515d4bd7adb185ff24ea5cc2cfcff953c19739ab',
 
   # WARNING: DO NOT EDIT MANUALLY
   # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py
@@ -63,7 +63,7 @@ vars = {
   'dart_http_throttle_tag': '1.0.2',
   'dart_intl_tag': '0.15.7',
   'dart_json_rpc_2_tag': '2.0.9',
-  'dart_linter_tag': '0.1.108',
+  'dart_linter_tag': '0.1.109',
   'dart_logging_tag': '0.11.3+2',
   'dart_markdown_tag': '2.1.1',
   'dart_matcher_tag': '0.12.3',

ci/licenses_golden/licenses_third_party

-Signature: 86dde6969586f924a0087fc5286f3709
+Signature: b188d23674242972284519c229250b8d
 
 UNUSED LICENSES: