Migrate test block 7 to Dart 2.0.

tests/corelib_2/error_stack_trace1_test.dart

Index: tests/corelib_2/error_stack_trace1_test.dart
diff --git a/tests/corelib_strong/error_stack_trace1_test.dart b/tests/corelib_2/error_stack_trace1_test.dart
similarity index 92%
rename from tests/corelib_strong/error_stack_trace1_test.dart
rename to tests/corelib_2/error_stack_trace1_test.dart
index 53df67173480c4a8a86e2df1d9da06b28cd058b4..17adde72b859af459697207a4dcad0b27a020d0d 100644
--- a/tests/corelib_strong/error_stack_trace1_test.dart
+++ b/tests/corelib_2/error_stack_trace1_test.dart
@@ -27,9 +27,9 @@ main() {
   bool hasThrown = false;
   try {
     B.Ba();
-  } catch (e) {
+  } catch (e, stackTrace) {
     hasThrown = true;
-    var trace = e.stackTrace.toString();
+    var trace = stackTrace.toString();
     print(trace);
     Expect.isTrue(trace.contains("Bc"));
     Expect.isTrue(trace.contains("Bb"));