Move main and isolate handling to enqueuer listeners.

pkg/compiler/lib/src/kernel/world_builder.dart

Index: pkg/compiler/lib/src/kernel/world_builder.dart
diff --git a/pkg/compiler/lib/src/kernel/world_builder.dart b/pkg/compiler/lib/src/kernel/world_builder.dart
index 38391d7351edbb177faa59e9f957370a07a4b748..f329a24c6cd3dadfa447320f068640935d5b0dd7 100644
--- a/pkg/compiler/lib/src/kernel/world_builder.dart
+++ b/pkg/compiler/lib/src/kernel/world_builder.dart
@@ -78,6 +78,18 @@ class KernelWorldBuilder extends KernelElementAdapterMixin {
     _typeConverter = new DartTypeConverter(this);
   }
 
+  KMethod get _mainFunction {
+    return _env.program.mainMethod != null
+        ? _getMethod(_env.program.mainMethod)
+        : null;
+  }
+
+  KLibrary get _mainLibrary {
+    return _env.program.mainMethod != null
+        ? _getLibrary(_env.program.mainMethod.enclosingLibrary)
+        : null;
+  }
+
   @override
   CommonElements get commonElements => _commonElements;
 
@@ -488,6 +500,12 @@ class KernelElementEnvironment implements ElementEnvironment {
   KernelElementEnvironment(this.worldBuilder);
 
   @override
+  LibraryEntity get mainLibrary => worldBuilder._mainLibrary;
+
+  @override
+  FunctionEntity get mainFunction => worldBuilder._mainFunction;
+
+  @override
   InterfaceType getThisType(ClassEntity cls) {
     return worldBuilder._getThisType(cls);
   }