Move CallbackBase::polymorphic_invoke_ into BindStateBase

base/callback_internal.h

Index: base/callback_internal.h
diff --git a/base/callback_internal.h b/base/callback_internal.h
index 0fe0b2d9e198716690365dc8d6a4c82508a79188..dfc6b3a19ed324a0e0951051ace039b0596f7412 100644
--- a/base/callback_internal.h
+++ b/base/callback_internal.h
@@ -31,9 +31,14 @@ class CallbackBase;
 // of bloat. Its only task is to call the destructor which can be done with a
 // function pointer.
 class BindStateBase {
+ public:
+  using InvokeFuncStorage = void(*)();
+
  protected:
-  explicit BindStateBase(void (*destructor)(BindStateBase*))
-      : ref_count_(0), destructor_(destructor) {}
+  BindStateBase(InvokeFuncStorage polymorphic_invoke,
+                void (*destructor)(BindStateBase*))
+      : polymorphic_invoke_(polymorphic_invoke),
+        ref_count_(0), destructor_(destructor) {}
   ~BindStateBase() = default;
 
  private:
@@ -44,6 +49,12 @@ class BindStateBase {
   void AddRef();
   void Release();
 
+  // 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.
+  InvokeFuncStorage polymorphic_invoke_;
+
   AtomicRefCount ref_count_;
 
   // Pointer to a function that will properly destroy |this|.
@@ -70,28 +81,25 @@ class BASE_EXPORT CallbackBase<CopyMode::MoveOnly> {
   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.
-  using InvokeFuncStorage = void(*)();
+  using InvokeFuncStorage = BindStateBase::InvokeFuncStorage;
 
   // Returns true if this callback equals |other|. |other| may be null.
   bool EqualsInternal(const CallbackBase& other) const;
 
   // Allow initializing of |bind_state_| via the constructor to avoid default
-  // initialization of the scoped_refptr.  We do not also initialize
-  // |polymorphic_invoke_| here because doing a normal assignment in the
-  // derived Callback templates makes for much nicer compiler errors.
+  // initialization of the scoped_refptr.
   explicit CallbackBase(BindStateBase* bind_state);
 
+  InvokeFuncStorage polymorphic_invoke() const {
+    return bind_state_->polymorphic_invoke_;
+  }
+
   // Force the destructor to be instantiated inside this translation unit so
   // that our subclasses will not get inlined versions.  Avoids more template
   // bloat.
   ~CallbackBase();
 
   scoped_refptr<BindStateBase> bind_state_;
-  InvokeFuncStorage polymorphic_invoke_ = nullptr;
 };
 
 // CallbackBase<Copyable> is a direct base class of Copyable Callbacks.