Revert of Remove IPC::BrokerableAttachment.

ipc/ipc_channel_reader.h

Index: ipc/ipc_channel_reader.h
diff --git a/ipc/ipc_channel_reader.h b/ipc/ipc_channel_reader.h
index 04a95dd260b7558305e323eec1f7c14527ca65cc..73cea04cca071f1b7585ef84924ec739316861af 100644
--- a/ipc/ipc_channel_reader.h
+++ b/ipc/ipc_channel_reader.h
@@ -12,6 +12,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/scoped_vector.h"
+#include "ipc/brokerable_attachment.h"
 #include "ipc/ipc_channel.h"
 #include "ipc/ipc_export.h"
 
@@ -100,9 +101,9 @@
   virtual bool ShouldDispatchInputMessage(Message* msg) = 0;
 
   // Overridden by subclasses to get attachments that are sent alongside the IPC
-  // channel.
+  // channel (as opposed to through a broker).
   // Returns true on success. False means a fatal channel error.
-  virtual bool GetAttachments(Message* msg) = 0;
+  virtual bool GetNonBrokeredAttachments(Message* msg) = 0;
 
   // Performs post-dispatch checks. Called when all input buffers are empty,
   // though there could be more data ready to be read from the OS.