IMediaSource: release mediabuffer after content is copied into shared memory.

Bug: 27362659
Bug: 26295488
Change-Id: I27a00440117f08acb0fb68347710c45927d4892a
diff --git a/media/libmedia/IMediaSource.cpp b/media/libmedia/IMediaSource.cpp
index b988c46..8376c0a 100644
--- a/media/libmedia/IMediaSource.cpp
+++ b/media/libmedia/IMediaSource.cpp
@@ -315,6 +315,9 @@
                     reply->writeInt32(offset);
                     reply->writeInt32(usedSize);
                     buf->meta_data()->writeToParcel(*reply);
+                    if (buf->mMemory == NULL) {
+                        buf->release();
+                    }
                 } else {
                     // buffer is small: copy it
                     if (buf->mMemory != NULL) {