Make base::internal::CallbackBase::is_null inline.

base/callback_internal.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.
 
 // This file contains utility functions and classes that help the
 // implementation, and management of the Callback objects.
 
 #ifndef BASE_CALLBACK_INTERNAL_H_
 #define BASE_CALLBACK_INTERNAL_H_
 
@@ skipping 19 matching lines @@
  protected:
   friend class RefCountedThreadSafe<BindStateBase>;
   virtual ~BindStateBase() {}
 };
 
 // Holds the Callback methods that don't require specialization to reduce
 // template bloat.
 class BASE_EXPORT CallbackBase {
  public:
   // Returns true if Callback is null (doesn't refer to anything).
-  bool is_null() const;
+  bool is_null() const { return bind_state_.get() == NULL; }
 
   // Returns the Callback into an uninitialized state.
   void Reset();
 
  protected:
   // In C++, it is safe to cast function pointers to function pointers of
   // another type. It is not okay to use void*. We create a InvokeFuncStorage
   // that that can store our function pointer, and then cast it back to
   // the original type on usage.
   typedef void(*InvokeFuncStorage)(void);
@@ skipping 118 matching lines @@
 
 template <typename T>
 typename enable_if<IsMoveOnlyType<T>::value, T>::type CallbackForward(T& t) {
   return t.Pass();
 }
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_CALLBACK_INTERNAL_H_