Make WDDestroyableResult<T> derive from WDResult<T>.

components/webdata/common/web_data_results.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_WEBDATA_COMMON_WEB_DATA_RESULTS_H_
 #define COMPONENTS_WEBDATA_COMMON_WEB_DATA_RESULTS_H_
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "components/webdata/common/webdata_export.h"
@@ skipping 63 matching lines @@
   T GetValue() const {
     return value_;
   }
 
  private:
   T value_;
 
   DISALLOW_COPY_AND_ASSIGN(WDResult);
 };
 
-template <class T> class WDDestroyableResult : public WDTypedResult {
+template <class T> class WDDestroyableResult : public WDResult<T> {
  public:
   WDDestroyableResult(
       WDResultType type,
       const T& v,
       const DestroyCallback& callback)
-      : WDTypedResult(type),
-        value_(v),
+      : WDResult<T>(type, v),
         callback_(callback) {
   }
 
   virtual ~WDDestroyableResult() {
   }
 
 
   virtual void Destroy()  override {
     if (!callback_.is_null()) {
       callback_.Run(this);
     }
   }
 
-  // Return a single value result.
-  T GetValue() const {
-    return value_;
-  }
-
  private:
-  T value_;
   DestroyCallback callback_;
 
   DISALLOW_COPY_AND_ASSIGN(WDDestroyableResult);
 };
 
 template <class T> class WDObjectResult : public WDTypedResult {
  public:
   explicit WDObjectResult(WDResultType type)
     : WDTypedResult(type) {
   }
 
   T* GetValue() const {
     return &value_;
   }
 
  private:
   // mutable to keep GetValue() const.
   mutable T value_;
   DISALLOW_COPY_AND_ASSIGN(WDObjectResult);
 };
 
 #endif  // COMPONENTS_WEBDATA_COMMON_WEB_DATA_RESULTS_H_