Roll engine with Dart 2.0 fixed-size integers (#13856)

* Roll engine to 37789650cb1254199426e5de5cc66c2ba63cbaf2
* Fix large integer literals in packages/flutter/test/services/message_codecs_test.dart

bin/internal/engine.version

-0a93f9ffbff17ab96616fe742ffb1c82dba2868e
+37789650cb1254199426e5de5cc66c2ba63cbaf2

packages/flutter/test/services/message_codecs_test.dart

@@ -35,8 +35,8 @@ void main() {
       _checkEncodeDecode<dynamic>(json, -7);
       _checkEncodeDecode<dynamic>(json, 98742923489);
       _checkEncodeDecode<dynamic>(json, -98742923489);
-      _checkEncodeDecode<dynamic>(json, 98740023429234899324932473298438);
-      _checkEncodeDecode<dynamic>(json, -98740023429234899324932473298438);
+      _checkEncodeDecode<dynamic>(json, 9223372036854775807);
+      _checkEncodeDecode<dynamic>(json, -9223372036854775807);
       _checkEncodeDecode<dynamic>(json, 3.14);
       _checkEncodeDecode<dynamic>(json, '');
       _checkEncodeDecode<dynamic>(json, 'hello');
@@ -49,7 +49,7 @@ void main() {
         false,
         -707,
         -7000000007,
-        -70000000000000000000000000000000000000000000000007,
+        -7000000000000000007,
         -3.14,
         '',
         'hello',
@@ -91,7 +91,7 @@ void main() {
       _checkEncoding<dynamic>(
         standard,
         -0x7fffffffffffffff - 2,
-        <int>[5, 17]..addAll('-8000000000000001'.codeUnits),
+        <int>[4, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f],
       );
       _checkEncoding<dynamic>(
         standard,
@@ -101,7 +101,7 @@ void main() {
       _checkEncoding<dynamic>(
         standard,
         0x7fffffffffffffff + 1,
-        <int>[5, 16]..addAll('8000000000000000'.codeUnits),
+        <int>[4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80],
       );
     });
     test('should encode sizes correctly at boundary cases', () {
@@ -134,8 +134,8 @@ void main() {
       _checkEncodeDecode<dynamic>(standard, -7);
       _checkEncodeDecode<dynamic>(standard, 98742923489);
       _checkEncodeDecode<dynamic>(standard, -98742923489);
-      _checkEncodeDecode<dynamic>(standard, 98740023429234899324932473298438);
-      _checkEncodeDecode<dynamic>(standard, -98740023429234899324932473298438);
+      _checkEncodeDecode<dynamic>(standard, 9223372036854775807);
+      _checkEncodeDecode<dynamic>(standard, -9223372036854775807);
       _checkEncodeDecode<dynamic>(standard, 3.14);
       _checkEncodeDecode<dynamic>(standard, double.INFINITY);
       _checkEncodeDecode<dynamic>(standard, double.NAN);
@@ -150,7 +150,7 @@ void main() {
         false,
         -707,
         -7000000007,
-        -70000000000000000000000000000000000000000000000007,
+        -7000000000000000007,
         -3.14,
         '',
         'hello',