Roll src/third_party/dart c6db986..245a574 (3 commits)

https://dart.googlesource.com/sdk.git/+log/c6db98667aa6..245a574301b1

git log c6db986..245a574 --date=short --first-parent --format='%ad %ae %s'
2020-05-12 sstrickl@google.com [vm] Make the ELF static symbol table a superset of the dynamic one.
2020-05-12 karlklose@google.com [presubmit] Add presubmit check for valid test matrix
2020-05-12 bkonyi@google.com [ VM / Service ] Remove package:path dependency from breakpoint_non_debuggable_library_test

Created with:
  gclient setdep -r src/third_party/dart@245a574301b1

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

Author: skia-flutter-autoroll

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': 'c6db98667aa67231d10d81c65b1640d4ef27a5ce',
+  'dart_revision': '245a574301b1de35541a8184567a780004450900',
 
   # 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

@@ -1,4 +1,4 @@
-Signature: 276baedd256f7d4fdf83e8afc14f8112
+Signature: 089dab6122ec08141d4ab4892d697b32
 
 UNUSED LICENSES: