isolates refactor: this change introduces 'dart:isolate' as a library. This is a

runtime/vm/dart_api_impl_test.cc

Index: runtime/vm/dart_api_impl_test.cc
diff --git a/runtime/vm/dart_api_impl_test.cc b/runtime/vm/dart_api_impl_test.cc
index aedc4874e4e46c97530035de0c62cc3fac8b4da6..b36c1cd7352b5eaf87f0d95ac77d1a44490b4f1d 100644
--- a/runtime/vm/dart_api_impl_test.cc
+++ b/runtime/vm/dart_api_impl_test.cc
@@ -3425,6 +3425,7 @@ UNIT_TEST_CASE(NewNativePort) {
 
   TestIsolateScope __test_isolate__;
   const char* kScriptChars =
+      "#import('dart:isolate');\n"
       "void callPort(SendPort port) {\n"
       "    port.call(null).receive((message, replyTo) {\n"
       "      throw new Exception(message);\n"
@@ -3481,6 +3482,7 @@ static bool RunLoopTestCallback(const char* name_prefix,
                                 void* data, char** error) {
   const char* kScriptChars =
       "#import('builtin');\n"
+      "#import('dart:isolate');\n"
       "class MyIsolate extends Isolate {\n"
       "  MyIsolate() : super() { }\n"
       "  void main() {\n"