Don't report redundant type errors in strong mode.

pkg/analyzer/lib/src/task/strong/info.dart

Index: pkg/analyzer/lib/src/task/strong/info.dart
diff --git a/pkg/analyzer/lib/src/task/strong/info.dart b/pkg/analyzer/lib/src/task/strong/info.dart
index 6169815f12b423841c35e64a6577f4a2d985cdad..a74ac60c9519f47997fc0157847a1fd984d3f0ec 100644
--- a/pkg/analyzer/lib/src/task/strong/info.dart
+++ b/pkg/analyzer/lib/src/task/strong/info.dart
@@ -34,6 +34,9 @@ class Cast extends Coercion {
   Cast(DartType fromType, DartType toType) : super(fromType, toType);
 }
 
+
+// TODO(rnystrom): Analyzer no longer produces or uses anything except Cast,
+// so this should be eliminated once DDC no longer uses it.
 // The abstract type of coercions mapping one type to another.
 // This class also exposes static builder functions which
 // check for errors and reduce redundant coercions to the identity.