dart2js: support tear-offs in the startup emitter.

pkg/compiler/lib/src/js_emitter/model.dart

Index: pkg/compiler/lib/src/js_emitter/model.dart
diff --git a/pkg/compiler/lib/src/js_emitter/model.dart b/pkg/compiler/lib/src/js_emitter/model.dart
index 1c147e146bd548fa09d58105ac66e213c4864a5e..be6919d74a893f8ed9c67a9cf21769b0ebd03d1d 100644
--- a/pkg/compiler/lib/src/js_emitter/model.dart
+++ b/pkg/compiler/lib/src/js_emitter/model.dart
@@ -380,7 +380,7 @@ abstract class Method {
 }
 
 /// A method that corresponds to a method in the original Dart program.
-class DartMethod extends Method {
+abstract class DartMethod extends Method {
   final bool needsTearOff;
   final js.Name tearOffName;
   final List<ParameterStubMethod> parameterStubs;
@@ -418,6 +418,8 @@ class DartMethod extends Method {
            (requiredParameterCount != null &&
             optionalParameterDefaultValues != null));
   }
+
+  bool get isStatic;
 }
 
 class InstanceMethod extends DartMethod {
@@ -451,6 +453,8 @@ class InstanceMethod extends DartMethod {
               functionType: functionType) {
     assert(isClosure != null);
   }
+
+  bool get isStatic => false;
 }
 
 /// A method that is generated by the backend and has not direct correspondence
@@ -506,6 +510,8 @@ class StaticDartMethod extends DartMethod implements StaticMethod {
               requiredParameterCount: requiredParameterCount,
               optionalParameterDefaultValues: optionalParameterDefaultValues,
               functionType: functionType);
+
+  bool get isStatic => true;
 }
 
 class StaticStubMethod extends StubMethod implements StaticMethod {