Create an option to disable type inference and type promotion.

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 8d7f4bf6f872c93b4a909ea341c452e6d2cf432a..05f1c75e8214639f78e7e889f5dc91541a266691 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
@@ -225,6 +225,35 @@ abstract class TypeInferrer {
   void inferParameterInitializer(Expression initializer, DartType declaredType);
 }
 
+/// Implementation of [TypeInferrer] which doesn't do any type inference.
+///
+/// This is intended for profiling, to ensure that type inference and type
+/// promotion do not slow down compilation too much.
+class TypeInferrerDisabled extends TypeInferrer {
+  @override
+  final typePromoter = new TypePromoterDisabled();
+
+  @override
+  String get uri => null;
+
+  @override
+  void inferFieldInitializer(DartType declaredType, Expression initializer) {}
+
+  @override
+  void inferFunctionBody(
+      DartType returnType, AsyncMarker asyncMarker, Statement body) {}
+
+  @override
+  void inferInitializer(Initializer initializer) {}
+
+  @override
+  void inferMetadata(List<Expression> annotations) {}
+
+  @override
+  void inferParameterInitializer(
+      Expression initializer, DartType declaredType) {}
+}
+
 /// Derived class containing generic implementations of [TypeInferrer].
 ///
 /// This class contains as much of the implementation of type inference as