Add type inference logic for "for-in" loops.

pkg/analyzer/test/src/task/strong/front_end_inference_test.dart

Index: pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
diff --git a/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart b/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
index fbd285988c5f5264b112a96e0ba2d0944a514a11..df8b30f91e681d5f97cc93a1f15281a04cce4281 100644
--- a/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
+++ b/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
@@ -404,6 +404,14 @@ class _InstrumentationVisitor extends RecursiveAstVisitor<Null> {
     }
   }
 
+  @override
+  visitDeclaredIdentifier(DeclaredIdentifier node) {
+    super.visitDeclaredIdentifier(node);
+    if (node.type == null) {
+      _recordType(node.identifier.offset, node.element.type);
+    }
+  }
+
   visitVariableDeclarationList(VariableDeclarationList node) {
     super.visitVariableDeclarationList(node);
     if (node.type == null) {