Implement override-based inference of instance fields.

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 018ffafaf5113be653a13722e96d2e622ca65275..278050ae7e0eca761621a55c98b71596d1b9b0aa 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
@@ -507,7 +507,7 @@ class _InstrumentationVisitor extends RecursiveAstVisitor<Null> {
         VariableElement element = variable.element;
         if (element is LocalVariableElement) {
           _recordType(variable.name.offset, element.type);
-        } else {
+        } else if (!element.isStatic || element.initializer != null) {
           _recordTopType(variable.name.offset, element.type);
         }
       }