Implement override-based type inference for instance methods.

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 da235affab3fae189599da7c3d7742c26095bc53..19b79685e44449a343300abf5aed8a5460c91b86 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
@@ -455,11 +455,15 @@ class _InstrumentationVisitor extends RecursiveAstVisitor<Null> {
   @override
   visitMethodDeclaration(MethodDeclaration node) {
     super.visitMethodDeclaration(node);
-    if (node.element.enclosingElement is ClassElement) {
-      if (node.isGetter && node.returnType == null) {
-        _recordTopType(node.name.offset, node.element.returnType);
+    if (node.element.enclosingElement is ClassElement && !node.isStatic) {
+      if (node.returnType == null) {
+        // For now, we skip inferred return types of setters.
+        // TODO(paulberry): fix this.
+        if (!node.isSetter) {
+          _recordTopType(node.name.offset, node.element.returnType);
+        }
       }
-      if (node.isSetter) {
+      if (node.parameters != null) {
         for (var parameter in node.parameters.parameters) {
           // Note: it's tempting to check `parameter.type == null`, but that
           // doesn't work because of function-typed formal parameter syntax.