Stub in more IPC attachment brokering functionality.

ipc/handle_attachment_win.h

Index: ipc/handle_attachment_win.h
diff --git a/ipc/handle_attachment_win.h b/ipc/handle_attachment_win.h
index b539907e8283e48f32b28bdfd98b0b892b551a31..7dd898ad54be0f3440732f2038c425b11fd3424c 100644
--- a/ipc/handle_attachment_win.h
+++ b/ipc/handle_attachment_win.h
@@ -5,6 +5,9 @@
 #ifndef IPC_HANDLE_ATTACHMENT_WIN_H_
 #define IPC_HANDLE_ATTACHMENT_WIN_H_
 
+#include <stdint.h>
+
+#include "base/process/process_handle.h"
 #include "ipc/brokerable_attachment.h"
 #include "ipc/ipc_export.h"
 
@@ -13,8 +16,30 @@ namespace internal {
 
 // This class represents a Windows HANDLE attached to a Chrome IPC message.
 class IPC_EXPORT HandleAttachmentWin : public BrokerableAttachment {
+ public:
+  // The wire format for this handle.
+  struct IPC_EXPORT WireFormat {
+    // The HANDLE that is intended for duplication, or the HANDLE that has been
+    // duplicated, depending on context.
+    // The type is int32_t instead of HANDLE because HANDLE gets typedefed to
+    // void*, whose size varies between 32 and 64-bit processes. Using a
+    // int32_t means that 64-bit processes will need to perform both up-casting
+    // and down-casting. This is performed using the appropriate Windows apis.
+    int32_t handle;
+    // The id of the destination process that the handle is duplicated into.
+    base::ProcessId destination_process;
+    AttachmentId attachment_id;
+  };
+
+  HandleAttachmentWin(const HANDLE& handle);
+
+  BrokerableType GetBrokerableType() const override;
+
+  // Returns the wire format of this attachment.
+  WireFormat GetWireFormat(const base::ProcessId& destination) const;
+
  private:
-  Type GetType() const override { return TYPE_WIN_HANDLE; }
+  ~HandleAttachmentWin() override;
   HANDLE handle_;
 };