AudioRecord::obtainBuffer() can return nonContig like AudioTrack

And fix error handling in both AudioRecord and AudioTrack.

Change-Id: I4853d736cc6d2c05de5b18b0eac62716edfa62ec
diff --git a/media/libmedia/AudioTrack.cpp b/media/libmedia/AudioTrack.cpp
index ce30c62..cfdb19c 100644
--- a/media/libmedia/AudioTrack.cpp
+++ b/media/libmedia/AudioTrack.cpp
@@ -1255,12 +1255,18 @@
 status_t AudioTrack::obtainBuffer(Buffer* audioBuffer, int32_t waitCount, size_t *nonContig)
 {
     if (audioBuffer == NULL) {
+        if (nonContig != NULL) {
+            *nonContig = 0;
+        }
         return BAD_VALUE;
     }
     if (mTransfer != TRANSFER_OBTAIN) {
         audioBuffer->frameCount = 0;
         audioBuffer->size = 0;
         audioBuffer->raw = NULL;
+        if (nonContig != NULL) {
+            *nonContig = 0;
+        }
         return INVALID_OPERATION;
     }