cpsir unittests: move all unittests into individual files and test runners.

tests/compiler/dart2js/cps_ir/input/constructor_4.dart

Index: tests/compiler/dart2js/cps_ir/input/constructor_4.dart
diff --git a/tests/compiler/dart2js/cps_ir/input/constructor_4.dart b/tests/compiler/dart2js/cps_ir/input/constructor_4.dart
new file mode 100644
index 0000000000000000000000000000000000000000..5f148542df02d44e5dd607d8b3ed8767ddf517f4
--- /dev/null
+++ b/tests/compiler/dart2js/cps_ir/input/constructor_4.dart
@@ -0,0 +1,20 @@
+class Base0 {
+  Base0() {
+    print('Base0');
+  }
+}
+class Base extends Base0 {
+  var x;
+  Base(x1) : x = (() => ++x1) {
+    print(x1); // use boxed x1
+  }
+}
+class Sub extends Base {
+  var y;
+  Sub(x, this.y) : super(x) {
+    print(x);
+  }
+}
+main() {
+  print(new Sub(1, 2).x);
+}