Fix potential NULL pointer deference in ToneGenerator destructor

Initial members in ToneGenerator so destructor can free
allocation properly.

Change-Id: I4a686084af48f99d2eefc33e56e3239846d3d34f
diff --git a/media/libmedia/ToneGenerator.cpp b/media/libmedia/ToneGenerator.cpp
index 253602d..a5ce487 100644
--- a/media/libmedia/ToneGenerator.cpp
+++ b/media/libmedia/ToneGenerator.cpp
@@ -798,7 +798,8 @@
 //        none
 //
 ////////////////////////////////////////////////////////////////////////////////
-ToneGenerator::ToneGenerator(audio_stream_type_t streamType, float volume, bool threadCanCallJava) {
+ToneGenerator::ToneGenerator(audio_stream_type_t streamType, float volume, bool threadCanCallJava)
+    : mpAudioTrack(NULL), mpToneDesc(NULL), mpNewToneDesc(NULL) {
 
     ALOGV("ToneGenerator constructor: streamType=%d, volume=%f", streamType, volume);
 
@@ -811,9 +812,6 @@
     mThreadCanCallJava = threadCanCallJava;
     mStreamType = streamType;
     mVolume = volume;
-    mpAudioTrack = NULL;
-    mpToneDesc = NULL;
-    mpNewToneDesc = NULL;
     // Generate tone by chunks of 20 ms to keep cadencing precision
     mProcessSize = (mSamplingRate * 20) / 1000;