Replace effect_callback_t to refactor

Test: Compiles
Bug: 199156212
Change-Id: I387995cca89b23b96d7662968be81b16d1139df8
diff --git a/media/jni/audioeffect/Visualizer.cpp b/media/jni/audioeffect/Visualizer.cpp
index 84a8d51..193a5d4 100644
--- a/media/jni/audioeffect/Visualizer.cpp
+++ b/media/jni/audioeffect/Visualizer.cpp
@@ -49,7 +49,7 @@
 }
 
 status_t Visualizer::set(int32_t priority,
-                         effect_callback_t cbf,
+                         legacy_callback_t cbf,
                          void* user,
                          audio_session_t sessionId,
                          audio_io_handle_t io,
diff --git a/media/jni/audioeffect/Visualizer.h b/media/jni/audioeffect/Visualizer.h
index aa07ce8..c402c10 100644
--- a/media/jni/audioeffect/Visualizer.h
+++ b/media/jni/audioeffect/Visualizer.h
@@ -75,8 +75,8 @@
      * See AudioEffect 'set' function for details on parameters.
      */
     status_t    set(int32_t priority = 0,
-                    effect_callback_t cbf = NULL,
-                    void* user = NULL,
+                    legacy_callback_t cbf = nullptr,
+                    void* user = nullptr,
                     audio_session_t sessionId = AUDIO_SESSION_OUTPUT_MIX,
                     audio_io_handle_t io = AUDIO_IO_HANDLE_NONE,
                     const AudioDeviceTypeAddr& device = {},