ipc: Add a new field num_brokered_attachments to the message header o…

…n Mac.

This will be used for attachment brokering on Mac.

BUG=535711

Review URL: https://codereview.chromium.org/1373133003

Cr-Commit-Position: refs/heads/master@{#351341}

ipc/ipc_message.cc

@@ -49,6 +49,9 @@ Message::~Message() {
 Message::Message() : base::Pickle(sizeof(Header)) {
   header()->routing = header()->type = 0;
   header()->flags = GetRefNumUpper24();
+#if defined(OS_MACOSX)
+  header()->num_brokered_attachments = 0;
+#endif
 #if defined(OS_POSIX)
   header()->num_fds = 0;
   header()->pad = 0;
@@ -62,6 +65,9 @@ Message::Message(int32_t routing_id, uint32_t type, PriorityValue priority)
   header()->type = type;
   DCHECK((priority & 0xffffff00) == 0);
   header()->flags = priority | GetRefNumUpper24();
+#if defined(OS_MACOSX)
+  header()->num_brokered_attachments = 0;
+#endif
 #if defined(OS_POSIX)
   header()->num_fds = 0;
   header()->pad = 0;

ipc/ipc_message.h

@@ -263,6 +263,12 @@ class IPC_EXPORT Message : public base::Pickle {
     int32_t routing;  // ID of the view that this message is destined for
     uint32_t type;    // specifies the user-defined message type
     uint32_t flags;   // specifies control flags for the message
+#if defined(OS_MACOSX)
+    // The number of brokered attachments included with this message. The
+    // ids of the brokered attachment ids are sent immediately after the pickled
+    // message, before the next pickled message is sent.
+    uint32_t num_brokered_attachments;
+#endif
 #if defined(OS_POSIX)
     uint16_t num_fds; // the number of descriptors included with this message
     uint16_t pad;     // explicitly initialize this to appease valgrind