Implement async/await/yield and async for-in

pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart

Index: pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
diff --git a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
index a865f1c6bd6394767f5ed38b483119306bc2bc27..7a76fd4ca7abc9e27b412a868480adbc3365fa10 100644
--- a/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
+++ b/pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart
@@ -405,6 +405,13 @@ class KernelAstAdapter {
       TypeMaskFactory.inferredReturnTypeForElement(
           _backend.helpers.traceFromException, _globalInferenceResults);
 
+  ir.Procedure get streamIteratorConstructor =>
+      kernel.functions[_backend.helpers.streamIteratorConstructor];
+
+  TypeMask get streamIteratorConstructorType =>
+      TypeMaskFactory.inferredReturnTypeForElement(
+          _backend.helpers.streamIteratorConstructor, _globalInferenceResults);
+
   ir.Procedure get mapLiteralUntypedMaker =>
       kernel.functions[_backend.helpers.mapLiteralUntypedMaker];
 
@@ -464,6 +471,12 @@ class KernelAstAdapter {
   ir.Class get objectClass =>
       kernel.classes[_compiler.commonElements.objectClass];
 
+  ir.Class get futureClass =>
+      kernel.classes[_compiler.commonElements.futureClass];
+
+  TypeMask makeSubtypeOfObject(ClosedWorld closedWorld) =>
+      new TypeMask.subclass(_compiler.commonElements.objectClass, closedWorld);
+
   ir.Procedure get currentIsolate =>
       kernel.functions[_backend.helpers.currentIsolate];