Change MethodInvocation.interfaceTarget from a Procedure to a Member.

pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
index 002ab8ef25c1dc1a510fddd932d88b92849e3ef6..5b66a5cfeb200a60c325fef1984f2d82648bda91 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
@@ -1035,7 +1035,7 @@ class KernelMapLiteral extends MapLiteral implements KernelExpression {
 class KernelMethodInvocation extends MethodInvocation
     implements KernelExpression {
   KernelMethodInvocation(Expression receiver, Name name, Arguments arguments,
-      [Procedure interfaceTarget])
+      [Member interfaceTarget])
       : super(receiver, name, arguments, interfaceTarget);
 
   KernelMethodInvocation.byReference(Expression receiver, Name name,
@@ -1069,12 +1069,7 @@ class KernelMethodInvocation extends MethodInvocation
           inferrer.instrumentation?.record(Uri.parse(inferrer.uri), fileOffset,
               'target', new InstrumentationValueForMember(interfaceMember));
         }
-        // interfaceTarget is currently required to be a procedure, so we skip
-        // if it's anything else.  TODO(paulberry): fix this - see
-        // https://codereview.chromium.org/2923653003/.
-        if (interfaceMember is Procedure) {
-          interfaceTarget = interfaceMember;
-        }
+        interfaceTarget = interfaceMember;
       }
       if (interfaceMember is Procedure) {
         isOverloadedArithmeticOperator = inferrer.typeSchemaEnvironment