Encrypted Media: Use uint32 for systemCode in SessionError.

ppapi/proxy/ppb_instance_proxy.cc

Index: ppapi/proxy/ppb_instance_proxy.cc
diff --git a/ppapi/proxy/ppb_instance_proxy.cc b/ppapi/proxy/ppb_instance_proxy.cc
index 80715ada31fcc045df84229a95aa3fdfcf786be0..4c2cc9315f5a279848c63bf494a08067e6cae890 100644
--- a/ppapi/proxy/ppb_instance_proxy.cc
+++ b/ppapi/proxy/ppb_instance_proxy.cc
@@ -571,7 +571,7 @@ void PPB_Instance_Proxy::SessionClosed(PP_Instance instance,
 void PPB_Instance_Proxy::SessionError(PP_Instance instance,
                                       uint32_t session_id,
                                       int32_t media_error,
-                                      int32_t system_code) {
+                                      uint32_t system_code) {
   dispatcher()->Send(new PpapiHostMsg_PPBInstance_SessionError(
       API_ID_PPB_INSTANCE, instance, session_id, media_error, system_code));
 }
@@ -1092,13 +1092,13 @@ void PPB_Instance_Proxy::OnHostMsgSessionClosed(PP_Instance instance,
 void PPB_Instance_Proxy::OnHostMsgSessionError(PP_Instance instance,
                                                uint32_t session_id,
                                                int32_t media_error,
-                                               int32_t system_error) {
+                                               uint32_t system_code) {
   if (!dispatcher()->permissions().HasPermission(PERMISSION_PRIVATE))
     return;
   EnterInstanceNoLock enter(instance);
   if (enter.succeeded()) {
     enter.functions()->SessionError(
-        instance, session_id, media_error, system_error);
+        instance, session_id, media_error, system_code);
   }
 }