fix more mixin tests to work in strong mode

tests/language_strong/mixin_type_parameters_mixin_extends_test.dart

Index: tests/language_strong/mixin_type_parameters_mixin_extends_test.dart
diff --git a/tests/language_strong/mixin_type_parameters_mixin_extends_test.dart b/tests/language_strong/mixin_type_parameters_mixin_extends_test.dart
index b1e9d3ffadb47663fb64cb46e8fb162ca1c94e01..69f3bbf7b0cee8297e46ac11581cb20d621a5930 100644
--- a/tests/language_strong/mixin_type_parameters_mixin_extends_test.dart
+++ b/tests/language_strong/mixin_type_parameters_mixin_extends_test.dart
@@ -29,7 +29,7 @@ class M<T> {
   static final bool checkedMode = computeCheckedMode();
   static bool computeCheckedMode() {
     try {
-      int x = "foo";
+      int x = "foo" as dynamic;
     } on Error {
       return true;
     }
@@ -50,32 +50,32 @@ class C3 extends S with M<String> {}
 main() {
   var c0 = new C0();
   Expect.isTrue(c0 is M);
-  Expect.isTrue(c0 is M<int>);
-  Expect.isTrue(c0 is M<String>);
+  Expect.isFalse(c0 is M<int>);
+  Expect.isFalse(c0 is M<String>);
   Expect.isTrue(c0.matches(c0));
   Expect.isTrue(c0.matches(42));
   Expect.isTrue(c0.matches("hello"));
 
   var c0_int = new C0<int>();
   Expect.isTrue(c0_int is M);
-  Expect.isTrue(c0_int is M<int>);
-  Expect.isTrue(c0_int is M<String>);
+  Expect.isFalse(c0_int is M<int>);
+  Expect.isFalse(c0_int is M<String>);
   Expect.isTrue(c0_int.matches(c0));
   Expect.isTrue(c0_int.matches(42));
   Expect.isTrue(c0_int.matches("hello"));
 
   var c0_String = new C0<String>();
   Expect.isTrue(c0_String is M);
-  Expect.isTrue(c0_String is M<int>);
-  Expect.isTrue(c0_String is M<String>);
+  Expect.isFalse(c0_String is M<int>);
+  Expect.isFalse(c0_String is M<String>);
   Expect.isTrue(c0_String.matches(c0));
   Expect.isTrue(c0_String.matches(42));
   Expect.isTrue(c0_String.matches("hello"));
 
   var c1 = new C1();
   Expect.isTrue(c1 is M);
-  Expect.isTrue(c1 is M<int>);
-  Expect.isTrue(c1 is M<String>);
+  Expect.isFalse(c1 is M<int>);
+  Expect.isFalse(c1 is M<String>);
   Expect.isTrue(c1.matches(c1));
   Expect.isTrue(c1.matches(42));
   Expect.isTrue(c1.matches("hello"));