Remove unused IPC::Message priority.

ipc/ipc_message.cc

Index: ipc/ipc_message.cc
diff --git a/ipc/ipc_message.cc b/ipc/ipc_message.cc
index cf3a65e077f08dc767f63150d48c848b79589419..b1eaaae11c0de5f15568510db1ba9c243554f419 100644
--- a/ipc/ipc_message.cc
+++ b/ipc/ipc_message.cc
@@ -50,12 +50,11 @@ Message::Message()
   InitLoggingVariables();
 }
 
-Message::Message(int32 routing_id, uint32 type, PriorityValue priority)
+Message::Message(int32 routing_id, uint32 type)
     : Pickle(sizeof(Header)) {
   header()->routing = routing_id;
   header()->type = type;
-  DCHECK((priority & 0xffffff00) == 0);
-  header()->flags = priority | GetRefNumUpper24();
+  header()->flags = GetRefNumUpper24();
 #if defined(OS_POSIX)
   header()->num_fds = 0;
   header()->pad = 0;
@@ -63,7 +62,8 @@ Message::Message(int32 routing_id, uint32 type, PriorityValue priority)
   InitLoggingVariables();
 }
 
-Message::Message(const char* data, int data_len) : Pickle(data, data_len) {
+Message::Message(const char* data, size_t data_len)
+    : Pickle(data, data_len) {
   InitLoggingVariables();
 }