Make BindStateBase constructor out-of-line

base/callback_internal.h

Index: base/callback_internal.h
diff --git a/base/callback_internal.h b/base/callback_internal.h
index dfc6b3a19ed324a0e0951051ace039b0596f7412..6aa5fa4e841657bcffd64fa541ecf92c8ce99677 100644
--- a/base/callback_internal.h
+++ b/base/callback_internal.h
@@ -30,15 +30,13 @@ class CallbackBase;
 // Creating a vtable for every BindState template instantiation results in a lot
 // of bloat. Its only task is to call the destructor which can be done with a
 // function pointer.
-class BindStateBase {
+class BASE_EXPORT BindStateBase {
  public:
   using InvokeFuncStorage = void(*)();
 
  protected:
   BindStateBase(InvokeFuncStorage polymorphic_invoke,
-                void (*destructor)(BindStateBase*))
-      : polymorphic_invoke_(polymorphic_invoke),
-        ref_count_(0), destructor_(destructor) {}
+                void (*destructor)(BindStateBase*));
   ~BindStateBase() = default;
 
  private: