IMediaSource: add supportReadMultiple().

Bug: 29331573
Change-Id: I7cdff44878bd93671e98fe11c99d17e82410cdcb
diff --git a/media/libmedia/IMediaSource.cpp b/media/libmedia/IMediaSource.cpp
index 7e40e4f..d2b4291 100644
--- a/media/libmedia/IMediaSource.cpp
+++ b/media/libmedia/IMediaSource.cpp
@@ -221,6 +221,10 @@
         return ret;
     }
 
+    bool supportReadMultiple() {
+        return true;
+    }
+
     virtual status_t pause() {
         ALOGV("pause");
         Parcel data, reply;