Add dart fix support to flutter_driver (#141300)

Part of https://github.com/flutter/flutter/issues/139249

This adds dart fix support plus fixes for APIs that are currently deprecated in the flutter_driver package.
https://dart.googlesource.com/external/github.com/flutter/flutter/+/9785718031dc0a4213b1c491fa8bb8d0516a9be2

DEPS

diff --git a/DEPS b/DEPS
index 5dcac15..7efbbb6 100644
--- a/DEPS
+++ b/DEPS
@@ -274,7 +274,7 @@
 
   'engine/src/third_party/dart': Var('dart_git') + '/sdk' + '@' + '19546dd72035a4f58fa1a67d80279b1ba4e3765d',
 
-  'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '13684ca4712b3e8d250a53aa921b716dcf91a706',
+  'flutter': Var('flutter_git') + '/mirrors/flutter' + '@' + '9785718031dc0a4213b1c491fa8bb8d0516a9be2',
 
   'engine/src/flutter/third_party/rapidjson':
    Var('flutter_git') + '/third_party/rapidjson' + '@' + 'ef3564c5c8824989393b87df25355baf35ff544b',

commits.json

diff --git a/commits.json b/commits.json
index c2118a5..7cf6cbb 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
   "engine/src/flutter":"c58f130cbfee49af6b1f26e63536a51c4a09a0f5",
   "engine/src/third_party/dart":"19546dd72035a4f58fa1a67d80279b1ba4e3765d",
-  "flutter":"13684ca4712b3e8d250a53aa921b716dcf91a706"
+  "flutter":"9785718031dc0a4213b1c491fa8bb8d0516a9be2"
 }
\ No newline at end of file