Roll src/third_party/dart 7376167b2a..b4688e9172 (4 commits)

dart-lang/sdk@b4688e9172 [vm, bytecode] Fix package splitting when main is empty.
dart-lang/sdk@56a28260fd [ Observatory ] Fixed issue where timeline save functionality was consistently failing
dart-lang/sdk@26b1aca71e [dartdevc] Canonicalizing partial instantiation constants
dart-lang/sdk@0a63bd4b0a diagnostic fix support for colors, iterables, lists, matrices

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': '7376167b2a1ec060283f815785656ec4b57aef67',
+  'dart_revision': 'b4688e917247bfc599325ca1ac389fc943c9b3fd',
 
   # 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: 27ab4449a8ce7bbfe64cd8dd9f70c761
+Signature: 07d9ca5e6de65cc92e31f805532a40a5
 
 UNUSED LICENSES: