Support for modular mixin resolution.

pkg/kernel/lib/core_types.dart

Index: pkg/kernel/lib/core_types.dart
diff --git a/pkg/kernel/lib/core_types.dart b/pkg/kernel/lib/core_types.dart
index 28ce858e35d891b08969c33208f083373b244464..72bf93d99b80eb52e44e468b9d3f33c33c2d0dc0 100644
--- a/pkg/kernel/lib/core_types.dart
+++ b/pkg/kernel/lib/core_types.dart
@@ -27,6 +27,33 @@ class CoreTypes {
   Class functionClass;
   Class invocationClass;
 
+  static final Map<String, List<String>> requiredClasses = {
+    'dart:core': [
+      'Object',
+      'Null',
+      'bool',
+      'int',
+      'num',
+      'double',
+      'String',
+      'List',
+      'Map',
+      'Iterable',
+      'Iterator',
+      'Symbol',
+      'Type',
+      'Function',
+      'Invocation',
+    ],
+    'dart:_internal': [
+      'Symbol',
+    ],
+    'dart:async': [
+      'Future',
+      'Stream',
+    ]
+  };
+
   Library getCoreLibrary(String uri) => _dartLibraries[uri]?.library;
 
   Class getCoreClass(String libraryUri, String className) {