Add WARN_UNUSED_RESULT to scoped_refptr::release.

base/memory/ref_counted.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 BASE_MEMORY_REF_COUNTED_H_
 #define BASE_MEMORY_REF_COUNTED_H_
 
 #include <cassert>
 
 #include "base/atomic_ref_count.h"
 #include "base/base_export.h"
+#include "base/compiler_specific.h"
 #include "base/threading/thread_collision_warner.h"
 
 namespace base {
 
 namespace subtle {
 
 class BASE_EXPORT RefCountedBase {
  public:
   bool HasOneRef() const { return ref_count_ == 1; }
 
@@ skipping 231 matching lines @@
   T* operator->() const {
     assert(ptr_ != NULL);
     return ptr_;
   }
 
   // Release a pointer.
   // The return value is the current pointer held by this object.
   // If this object holds a NULL pointer, the return value is NULL.
   // After this operation, this object will hold a NULL pointer,
   // and will not own the object any more.
-  T* release() {
+  T* release() WARN_UNUSED_RESULT {
     T* retVal = ptr_;
     ptr_ = NULL;
     return retVal;
   }
 
   scoped_refptr<T>& operator=(T* p) {
     // AddRef first so that self assignment should work
     if (p)
       p->AddRef();
     T* old_ptr = ptr_;
@@ skipping 27 matching lines @@
 };
 
 // Handy utility for creating a scoped_refptr<T> out of a T* explicitly without
 // having to retype all the template arguments
 template <typename T>
 scoped_refptr<T> make_scoped_refptr(T* t) {
   return scoped_refptr<T>(t);
 }
 
 #endif  // BASE_MEMORY_REF_COUNTED_H_