Avoid calling Dart_New in engine - it's slow. #50997
Description
Devicelab cull_opacity_perf__timeline_summary test failing with 30 second timeout exception.
2020-02-18T15:06:37.185691: stderr: [ +37 ms] VMServiceFlutterDriver: Waiting for service extension
2020-02-18T15:06:37.354258: stderr: [ +168 ms] VMServiceFlutterDriver: Connected to Flutter application.
2020-02-18T15:07:06.827425: stdout: [+29473 ms] 00:30 �[32m+0�[0m�[31m -1�[0m: cull_opacity_perf �[1m�[31m[E]�[0m�[0m
2020-02-18T15:07:06.829451: stdout: [ +2 ms] TimeoutException after 0:00:30.000000: Test timed out after 30 seconds. See https://pub.dev/packages/test#timeouts
cull_opacity_perf__timeline_summary_bcacd06_2.log
Failing on engine roll bcacd06