Add missing abstract method to interface

Fixes analyzer warning.

Bug:
Change-Id: I404855f42190be10a11658cf8f144c2627b73117
Reviewed-on: https://dart-review.googlesource.com/6820
Reviewed-by: Stephen Adams <sra@google.com>

pkg/compiler/lib/src/kernel/element_map.dart

@@ -352,6 +352,9 @@ abstract class KernelToTypeInferenceMap {
   /// Returns the inferred receiver type of the dynamic [read].
   TypeMask typeOfGet(ir.PropertyGet read);
 
+  /// Returns the inferred receiver type of the direct [read].
+  TypeMask typeOfDirectGet(ir.DirectPropertyGet read);
+
   /// Returns the inferred receiver type of the dynamic [write].
   TypeMask typeOfSet(ir.PropertySet write, ClosedWorld closedWorld);