Revert of Remove IPC::BrokerableAttachment.

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 ef3b89652caf8c2e0fa332b3af659d6a3571545a..cfe56a36bd81c95373b70d9f43f905f259d8f236 100644
--- a/ipc/handle_attachment_win.h
+++ b/ipc/handle_attachment_win.h
@@ -8,16 +8,48 @@
 #include <stdint.h>
 
 #include "base/process/process_handle.h"
+#include "ipc/brokerable_attachment.h"
 #include "ipc/handle_win.h"
 #include "ipc/ipc_export.h"
-#include "ipc/ipc_message_attachment.h"
 
 namespace IPC {
 namespace internal {
 
 // This class represents a Windows HANDLE attached to a Chrome IPC message.
-class IPC_EXPORT HandleAttachmentWin : public MessageAttachment {
+class IPC_EXPORT HandleAttachmentWin : public BrokerableAttachment {
  public:
+  // The wire format for this handle.
+  struct IPC_EXPORT WireFormat {
+    // IPC translation requires that classes passed through IPC have a default
+    // constructor.
+    WireFormat()
+        : handle(0),
+          destination_process(0),
+          permissions(HandleWin::INVALID) {}
+
+    WireFormat(int32_t handle,
+               const base::ProcessId& destination_process,
+               HandleWin::Permissions permissions)
+        : handle(handle),
+          destination_process(destination_process),
+          permissions(permissions) {}
+
+    // 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.
+    // A value of 0 is equivalent to an invalid handle.
+    int32_t handle;
+
+    // The id of the destination process that the handle is duplicated into.
+    base::ProcessId destination_process;
+
+    // The permissions to use when duplicating the handle.
+    HandleWin::Permissions permissions;
+  };
+
   // This constructor makes a copy of |handle| and takes ownership of the
   // result. Should only be called by the sender of a Chrome IPC message.
   HandleAttachmentWin(const HANDLE& handle, HandleWin::Permissions permissions);
@@ -29,7 +61,14 @@
   // receiver of a Chrome IPC message.
   HandleAttachmentWin(const HANDLE& handle, FromWire from_wire);
 
-  Type GetType() const override;
+  // This constructor takes ownership of |wire_format.handle| without making a
+  // copy. Should only be called by the receiver of a Chrome IPC message.
+  explicit HandleAttachmentWin(const WireFormat& wire_format);
+
+  BrokerableType GetBrokerableType() const override;
+
+  // Returns the wire format of this attachment.
+  WireFormat GetWireFormat(const base::ProcessId& destination) const;
 
   HANDLE get_handle() const { return handle_; }