Remove IPC::Endpoint.

ipc/ipc_message.cc

Index: ipc/ipc_message.cc
diff --git a/ipc/ipc_message.cc b/ipc/ipc_message.cc
index eef4b755025723cdf707b960d19ed99d0714ba5c..008401f14f358c620a7e6a206bb9fb969fa63220 100644
--- a/ipc/ipc_message.cc
+++ b/ipc/ipc_message.cc
@@ -78,12 +78,10 @@ Message::Message(const char* data, int data_len)
 Message::Message(const Message& other) : base::Pickle(other) {
   Init();
   attachment_set_ = other.attachment_set_;
-  sender_pid_ = other.sender_pid_;
 }
 
 void Message::Init() {
   dispatch_error_ = false;
-  sender_pid_ = base::kNullProcessId;
 #ifdef IPC_MESSAGE_LOG_ENABLED
   received_time_ = 0;
   dont_log_ = false;
@@ -94,7 +92,6 @@ void Message::Init() {
 Message& Message::operator=(const Message& other) {
   *static_cast<base::Pickle*>(this) = other;
   attachment_set_ = other.attachment_set_;
-  sender_pid_ = other.sender_pid_;
   return *this;
 }