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..f1a31ea89c2dd9be2feec1cd0663a41939fbba24 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));
 }
@@ -1092,7 +1092,7 @@ 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_error) {
   if (!dispatcher()->permissions().HasPermission(PERMISSION_PRIVATE))
     return;
   EnterInstanceNoLock enter(instance);