Add type inference of annotations.

pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart

Index: pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
diff --git a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
index d7761fe769be537f40c18f8dbbf2bbf56fd30536..a44e76fada8c41e63ca20e98eedfc4301a719108 100644
--- a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
@@ -217,6 +217,9 @@ abstract class TypeInferrer {
   /// Performs type inference on the given constructor initializer.
   void inferInitializer(Initializer initializer);
 
+  /// Performs type inference on the given metadata annotations.
+  void inferMetadata(List<Expression> annotations);
+
   /// Performs type inference on the given function parameter initializer
   /// expression.
   void inferParameterInitializer(Expression initializer, DartType declaredType);
@@ -774,6 +777,15 @@ abstract class TypeInferrerImpl extends TypeInferrer {
     return typeNeeded ? function.functionType : null;
   }
 
+  @override
+  void inferMetadata(List<Expression> annotations) {
+    if (annotations != null) {
+      for (var annotation in annotations) {
+        inferExpression(annotation, null, false);
+      }
+    }
+  }
+
   /// Performs the core type inference algorithm for method invocations (this
   /// handles both null-aware and non-null-aware method invocations).
   DartType inferMethodInvocation(