kernel -> ssa: support static invocations and variable gets

tests/compiler/dart2js/kernel/simple_function_test.dart

 import 'package:test/test.dart';
 
 import 'helper.dart' show check;
 
 main() {
   group('compile function that returns a value', () {
     test('constant int', () {
-      return check("main() { return 1; }");
+      return check('main() { return 1; }');
     });
 
     test('constant double', () {
-      return check("main() { return 1.0; }");
+      return check('main() { return 1.0; }');
     });
 
     test('constant string', () {
-      return check("main() { return 'hello'; }");
+      return check('main() { return "hello"; }');
     });
 
     test('constant bool', () {
-      return check("main() { return true; }");
+      return check('main() { return true; }');
     });
 
     test('constant symbol', () {
-      return check("main() { return #hello; }");
+      return check('main() { return #hello; }');
     });
 
     test('null', () {
-      return check("main() { return null; }");
+      return check('main() { return null; }');
     });
   });
+
+  test('compile function that returns its argument', () {
+    String code = '''
+      foo(x) {
+        return x;
+      }
+
+      main() {
+        foo(1);
+      }''';
+    return check(code, entry: 'foo');
+  });
 }