Add 'dash' as a compatible brand

Per the spec, the 'dash' brand indicates support for the concatenation
of an Initialization Segment and a single Indexed Media Segment. Since
we support this, add 'dash' as a supported brand to improve compatibility.

Bug: 63390273
Test: played 'dash' brand file
Change-Id: Ifb38337200857f190085bda030434d7f56a817f3
diff --git a/media/libstagefright/MPEG4Extractor.cpp b/media/libstagefright/MPEG4Extractor.cpp
index afcf661..4c0bb39 100644
--- a/media/libstagefright/MPEG4Extractor.cpp
+++ b/media/libstagefright/MPEG4Extractor.cpp
@@ -5014,6 +5014,7 @@
         FOURCC('3', 'g', 'p', '4'),
         FOURCC('m', 'p', '4', '1'),
         FOURCC('m', 'p', '4', '2'),
+        FOURCC('d', 'a', 's', 'h'),
 
         // Won't promise that the following file types can be played.
         // Just give these file types a chance.