Devirtualize base::BindState to save ~1% of Chrome's binary size (~1MB)

base/callback.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_CALLBACK_H_
 #define BASE_CALLBACK_H_
 
 #include "base/callback_forward.h"
 #include "base/callback_internal.h"
 #include "base/template_util.h"
@@ skipping 349 matching lines @@
 namespace internal {
 template <typename Runnable, typename RunType, typename BoundArgsType>
 struct BindState;
 }  // namespace internal
 
 template <typename R, typename... Args>
 class Callback<R(Args...)> : public internal::CallbackBase {
  public:
   typedef R(RunType)(Args...);
 
-  Callback() : CallbackBase(NULL) { }
+  Callback() {}
 
   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
   // return the exact Callback<> type.  See base/bind.h for details.
   template <typename Runnable, typename BindRunType, typename BoundArgsType>
   Callback(internal::BindState<Runnable, BindRunType,
            BoundArgsType>* bind_state)
       : CallbackBase(bind_state) {
     // Force the assignment to a local variable of PolymorphicInvoke
     // so the compiler will typecheck that the passed in Run() method has
     // the correct type.
     PolymorphicInvoke invoke_func =
         &internal::BindState<Runnable, BindRunType, BoundArgsType>
             ::InvokerType::Run;
     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
   }
 
   bool Equals(const Callback& other) const {
     return CallbackBase::Equals(other);
   }
 
   R Run(typename internal::CallbackParamTraits<Args>::ForwardType... args)
       const {
     PolymorphicInvoke f =
         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 
-    return f(bind_state_.get(), internal::CallbackForward(args)...);
+    return f(bind_state_, internal::CallbackForward(args)...);
   }
 
  private:
   typedef R(*PolymorphicInvoke)(
       internal::BindStateBase*,
       typename internal::CallbackParamTraits<Args>::ForwardType...);
 };
 
 // Syntactic sugar to make Callback<void(void)> easier to declare since it
 // will be used in a lot of APIs with delayed execution.
 typedef Callback<void(void)> Closure;
 
 }  // namespace base
 
 #endif  // BASE_CALLBACK_H_