Make static tear-off closures a class, like instance tear-off closures.

tests/compiler/dart2js/ssa_phi_codegen_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Test that parameters keep their names in the output.
 
 import 'compiler_helper.dart';
 
 const String TEST_ONE = r"""
 void foo(bar) {
   var a = 1;
   if (bar) {
     a = 2;
   } else {
     a = 3;
   }
   print(a);
+  print(a);
 }
 """;
 
 const String TEST_TWO = r"""
 void main() {
   var t = 0;
   for (var i = 0; i == 0; i = i + 1) {
     t = t + 10;
   }
   print(t);
@@ skipping 50 matching lines @@
   compileAndDoNotMatchFuzzy(TEST_THREE, 'foo', '(x) = \1');
   compileAndMatchFuzzy(TEST_THREE, 'foo', 'return x');
   // Check that a store just after the declaration of the local
   // only generates one instruction.
   compileAndMatchFuzzy(TEST_THREE, 'foo', 'x = 42');
 
   compileAndDoNotMatchFuzzy(TEST_FOUR, 'foo', '(x) = \1;');
 
   compileAndDoNotMatch(TEST_FIVE, 'main', new RegExp('hash0'));
 }