MediaCas: add MediaCasService

This CL adds API only without implementation.

bug: 22804304
Change-Id: Ibb5a29cc616ec0af81957b2bfe1419c482591753
diff --git a/drm/libmediadrm/SharedLibrary.cpp b/drm/libmediadrm/SharedLibrary.cpp
index 74b3a71..bebafa8 100644
--- a/drm/libmediadrm/SharedLibrary.cpp
+++ b/drm/libmediadrm/SharedLibrary.cpp
@@ -43,6 +43,9 @@
         if (!mLibHandle) {
             return NULL;
         }
+        // Clear last error before we load the symbol again,
+        // in case the caller didn't retrieve it.
+        (void)dlerror();
         return dlsym(mLibHandle, symbol);
     }