Enable flattening/unflattening with custom unflatten procs

include/core/SkFlattenable.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkFlattenable_DEFINED
 #define SkFlattenable_DEFINED
 
@@ skipping 74 matching lines @@
     typedef sk_sp<SkFlattenable> (*Factory)(SkReadBuffer&);
 
     SkFlattenable() {}
 
     /** Implement this to return a factory function pointer that can be called
      to recreate your class given a buffer (previously written to by your
      override of flatten().
      */
     virtual Factory getFactory() const = 0;
 
-    /** Returns the name of the object's class
-      */
-    const char* getTypeName() const { return FactoryToName(getFactory()); }
+    /**
+     *  Returns the name of the object's class.
+     *
+     *  Subclasses should override this function if they intend to provide
+     *  support for flattening without using the global registry.
+     *
+     *  If the flattenable is registered, there is no need to override.
+     */
+    virtual const char* getTypeName() const { return FactoryToName(getFactory()); }
 
     static Factory NameToFactory(const char name[]);
     static const char* FactoryToName(Factory);
     static bool NameToType(const char name[], Type* type);
 
     static void Register(const char name[], Factory, Type);
 
     /**
      *  Override this if your subclass needs to record data that it will need to recreate itself
      *  from its CreateProc (returned by getFactory()).
      */
     virtual void flatten(SkWriteBuffer&) const {}
 
 protected:
     class PrivateInitializer {
     public:
         static void InitCore();
         static void InitEffects();
     };
 
 private:
     static void InitializeFlattenablesIfNeeded();
 
     friend class SkGraphics;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif