Log the runtime type of messages

test/codegen/expect/DeltaBlue.txt

Index: test/codegen/expect/DeltaBlue.txt
diff --git a/test/codegen/expect/DeltaBlue.txt b/test/codegen/expect/DeltaBlue.txt
index bf86267761f938267217d995598945f98aa4ba14..888d0b6c02e16fd3fdd42d221c3db453a1d7bf3b 100644
--- a/test/codegen/expect/DeltaBlue.txt
+++ b/test/codegen/expect/DeltaBlue.txt
@@ -1,16 +1,16 @@
 // Messages from compiling DeltaBlue.dart
-warning: line 63, column 7 of test/codegen/BenchmarkBase.dart: f() requires dynamic invoke
+warning: line 63, column 7 of test/codegen/BenchmarkBase.dart: [DynamicInvoke] f() requires dynamic invoke
       f();
       ^^^
-info: line 130, column 18 of test/codegen/DeltaBlue.dart: mark (dynamic) will need runtime check to cast to type int
+info: line 130, column 18 of test/codegen/DeltaBlue.dart: [DownCast] mark (dynamic) will need runtime check to cast to type int
     chooseMethod(mark);
                  ^^^^
-info: line 137, column 16 of test/codegen/DeltaBlue.dart: mark (dynamic) will need runtime check to cast to type int
+info: line 137, column 16 of test/codegen/DeltaBlue.dart: [DownCast] mark (dynamic) will need runtime check to cast to type int
     markInputs(mark);
                ^^^^
-info: line 142, column 37 of test/codegen/DeltaBlue.dart: mark (dynamic) will need runtime check to cast to type int
+info: line 142, column 37 of test/codegen/DeltaBlue.dart: [DownCast] mark (dynamic) will need runtime check to cast to type int
     if (!planner.addPropagate(this, mark)) print("Cycle encountered");
                                     ^^^^
-info: line 143, column 16 of test/codegen/DeltaBlue.dart: mark (dynamic) will need runtime check to cast to type int
+info: line 143, column 16 of test/codegen/DeltaBlue.dart: [DownCast] mark (dynamic) will need runtime check to cast to type int
     out.mark = mark;
                ^^^^