Don't depend on String8 cast to C string [cas]

Bug: 295394788
Test: m checkbuild
Change-Id: I82c94f0a720957c443f92b030214c6d2c47bf009
diff --git a/cas/1.0/default/DescramblerImpl.cpp b/cas/1.0/default/DescramblerImpl.cpp
index 6b730eb..6d7c304 100644
--- a/cas/1.0/default/DescramblerImpl.cpp
+++ b/cas/1.0/default/DescramblerImpl.cpp
@@ -79,7 +79,7 @@
         return false;
     }
 
-    return holder->requiresSecureDecoderComponent(String8(mime.c_str()));
+    return holder->requiresSecureDecoderComponent(mime.c_str());
 }
 
 static inline bool validateRangeForSize(