Use String8/16 c_str

Bug: 295394788
Test: make checkbuild
Change-Id: I538720d4de2dcc038b417048209782ff605b7e30
diff --git a/media/jni/android_media_MediaPlayer.cpp b/media/jni/android_media_MediaPlayer.cpp
index a548a47..43de378 100644
--- a/media/jni/android_media_MediaPlayer.cpp
+++ b/media/jni/android_media_MediaPlayer.cpp
@@ -1214,7 +1214,7 @@
     String8 vendorMessage;
     if (err >= ERROR_DRM_VENDOR_MIN && err <= ERROR_DRM_VENDOR_MAX) {
         vendorMessage = String8::format("DRM vendor-defined error: %d", err);
-        drmMessage = vendorMessage.string();
+        drmMessage = vendorMessage.c_str();
     }
 
     if (err == BAD_VALUE) {
@@ -1240,7 +1240,7 @@
                 msg = drmMessage;
             } else {
                 errbuf = String8::format("%s: %s", msg, drmMessage);
-                msg = errbuf.string();
+                msg = errbuf.c_str();
             }
         }
         throwDrmStateException(env, msg, err);