Make sure that the trackId starts from 1

o this patch avoids sending incorrect track events to applications because
  track events contain the trackId

Change-Id: I1cf054da8ab413d31a5b7fe8ed729486d1475c46
diff --git a/media/libstagefright/MPEG4Writer.cpp b/media/libstagefright/MPEG4Writer.cpp
index 5aad99f..86477ba 100755
--- a/media/libstagefright/MPEG4Writer.cpp
+++ b/media/libstagefright/MPEG4Writer.cpp
@@ -428,7 +428,7 @@
         ALOGE("Attempt to add source AFTER recording is started");
         return UNKNOWN_ERROR;
     }
-    Track *track = new Track(this, source, mTracks.size());
+    Track *track = new Track(this, source, 1 + mTracks.size());
     mTracks.push_back(track);
 
     return OK;
@@ -2693,7 +2693,7 @@
     mOwner->writeInt32(0x07);          // version=0, flags=7
     mOwner->writeInt32(now);           // creation time
     mOwner->writeInt32(now);           // modification time
-    mOwner->writeInt32(mTrackId + 1);  // track id starts with 1
+    mOwner->writeInt32(mTrackId);      // track id starts with 1
     mOwner->writeInt32(0);             // reserved
     int64_t trakDurationUs = getDurationUs();
     int32_t mvhdTimeScale = mOwner->getTimeScale();