Make sure the ThrottledSource reports the proper mime type

of the underlying source.

Change-Id: I7cfd5c9f10d4b07781ed82fbdc9bf3db2e86cf84

Author: theandi666

media/libstagefright/include/ThrottledSource.h

@@ -35,6 +35,11 @@ struct ThrottledSource : public DataSource {
     virtual status_t getSize(off64_t *size);
     virtual uint32_t flags();
 
+    virtual String8 getMIMEType() const {
+        return mSource->getMIMEType();
+    }
+
+
 private:
     Mutex mLock;