[dart2dart] Cut declaration types by default if we check that it is safe to do so.

tests/compiler/dart2js/unparser_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.
 
 #import('dart:uri');
 #import('parser_helper.dart');
 #import('mock_compiler.dart');
 #import("../../../lib/compiler/compiler.dart");
 #import("../../../lib/compiler/implementation/leg.dart", prefix:'leg');
 #import("../../../lib/compiler/implementation/dart_backend/dart_backend.dart");
@@ skipping 17 matching lines @@
 interface num {}
 interface int extends num {}
 interface double extends num {}
 interface String {}
 interface Function {}
 interface List {}
 interface Map {}
 interface Closure {}
 interface Dynamic_ {}
 interface Null {}
+interface TypeError {}
 class Math {
   static double parseDouble(String s) => 1.0;
 }
 ''';
 
 const ioLib = r'''
 #library('io');
 class Platform {
   static int operatingSystem;
 }
@@ skipping 672 matching lines @@
   void foo1(a,b) {
     void foo2(c,d) {
        var E = a;
     }
     foo2(b, a);
   }
   foo1(a, 8);
 }
 ''';
   var expectedResult =
-      'main(){var A=7;void B(A,C){void D(E,F){var G=A;}D(C,A);}B(A,8);}';
+      'main(){var A=7; B(A,C){ D(E,F){var G=A;}D(C,A);}B(A,8);}';
   testDart2Dart(src,
       (String result) { Expect.equals(expectedResult, result); }, minify: true);
 }
 
 testParametersMinified() {
   var src = '''
 class A {
   var a;
   static foo(arg1) {
     // Should not rename arg1 to a.
@@ skipping 106 matching lines @@
   testDoubleMains();
   testInterfaceDefaultAnotherLib();
   testStaticAccessIoLib();
   testLocalFunctionPlaceholder();
   testMinification();
   testClosureLocalsMinified();
   testParametersMinified();
   testTypeVariablesInDifferentLibraries();
   testDeclarationTypePlaceholders();
 }