[vm, gc] Refactor common setup code for safepoint tasks.

TEST=ci
Change-Id: I48239d109330f163307f4849ebc4139f95f524ec
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/385620
Reviewed-by: Alexander Aprelev <aam@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

https://dart.googlesource.com/sdk/+/4de0c76294bc0a4e30cf23210aa4654710155efa

DEPS

diff --git a/DEPS b/DEPS
index e83034b..ad47ce3 100644
--- a/DEPS
+++ b/DEPS
@@ -282,7 +282,7 @@
 
   'engine/src/flutter': Var('flutter_git') + '/mirrors/engine' + '@' + '8a5af19a43f3336e64888037eb69553c86680f3a',
 
-  'engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + '2a96956cd3aa7603bf74cc77bc502494c37bd178',
+  'engine/src/flutter/third_party/dart': Var('dart_git') + '/sdk' + '@' + '4de0c76294bc0a4e30cf23210aa4654710155efa',
 
   'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '96ba3c555afb8bfd5a53ba35e47a7e91943c3167',
 

commits.json

diff --git a/commits.json b/commits.json
index bd25c47..97ca3dd 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
   "engine/src/flutter":"8a5af19a43f3336e64888037eb69553c86680f3a",
-  "engine/src/flutter/third_party/dart":"2a96956cd3aa7603bf74cc77bc502494c37bd178",
+  "engine/src/flutter/third_party/dart":"4de0c76294bc0a4e30cf23210aa4654710155efa",
   "flutter":"96ba3c555afb8bfd5a53ba35e47a7e91943c3167"
 }
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