add support for native methods in class

pkg/analyzer/lib/src/fasta/ast_builder.dart

Index: pkg/analyzer/lib/src/fasta/ast_builder.dart
diff --git a/pkg/analyzer/lib/src/fasta/ast_builder.dart b/pkg/analyzer/lib/src/fasta/ast_builder.dart
index 6425a7ebfb9c4b0af48f8e45f6df0836d6273029..aa47114daea0367ba5b2f4287365f18e80705062 100644
--- a/pkg/analyzer/lib/src/fasta/ast_builder.dart
+++ b/pkg/analyzer/lib/src/fasta/ast_builder.dart
@@ -1290,7 +1290,7 @@ class AstBuilder extends ScopeListener {
 
   @override
   void handleNativeClause(Token nativeToken, bool hasName) {
-    push(ast.nativeClause(nativeToken, hasName ? pop() : null));
+    if (!hasName) push(NullValue.StringLiteral);
   }
 
   @override
@@ -1304,7 +1304,12 @@ class AstBuilder extends ScopeListener {
       Token endToken) {
     debugEvent("ClassDeclaration");
     _ClassBody body = pop();
-    NativeClause nativeClause = nativeToken != null ? pop() : null;
+    NativeClause nativeClause;
+    if (nativeToken != null) {
+      var nativeName = pop();
+      nativeClause = ast.nativeClause(nativeToken,
+          nativeName == NullValue.StringLiteral ? null : nativeName);
+    }
     ImplementsClause implementsClause;
     if (implementsKeyword != null) {
       List<TypeName> interfaces = popList(interfacesCount);
@@ -1607,9 +1612,22 @@ class AstBuilder extends ScopeListener {
   }
 
   @override
-  void endMethod(Token getOrSet, Token beginToken, Token endToken) {
+  void endMethod(
+      Token getOrSet, Token beginToken, Token nativeToken, Token endToken) {
     debugEvent("Method");
     FunctionBody body = pop();
+    if (nativeToken != null) {
+      var nativeName = pop();
+      if (nativeName == NullValue.StringLiteral) {
+        nativeName = null;
+      }
+      if (body is EmptyFunctionBody) {
+        body = ast.nativeFunctionBody(nativeToken, nativeName, body.endToken);
+      } else {
+        // TODO(danrubel): Report error if native clause is used with
+        // non-empty function body.
+      }
+    }
     ConstructorName redirectedConstructor = null; // TODO(paulberry)
     List<ConstructorInitializer> initializers = pop() ?? const [];
     Token separator = pop();