Consolidate the code that replaces a TypeParameter with its bound.

pkg/analyzer/lib/dart/element/type.dart

Index: pkg/analyzer/lib/dart/element/type.dart
diff --git a/pkg/analyzer/lib/dart/element/type.dart b/pkg/analyzer/lib/dart/element/type.dart
index f49c170544e92ea42e4bd5d74696a588f9ac9531..3ff2ce83b166c11deb006c93d0a2f6897bfc3b5d 100644
--- a/pkg/analyzer/lib/dart/element/type.dart
+++ b/pkg/analyzer/lib/dart/element/type.dart
@@ -150,6 +150,15 @@ abstract class DartType {
    */
   DartType substitute2(
       List<DartType> argumentTypes, List<DartType> parameterTypes);
+
+  /**
+   * If this type is a [TypeParameterType], returns its bound if it has one, or
+   * [objectType] otherwise.
+   *
+   * For any other type, returns `this`. Applies recursively -- if the bound is
+   * itself a type parameter, that is resolved too.
+   */
+  DartType resolveToBound(DartType objectType);
 }
 
 /**