Update content module for IPC attachment brokering.

content/public/child/child_thread.h

Index: content/public/child/child_thread.h
diff --git a/content/public/child/child_thread.h b/content/public/child/child_thread.h
index 6293ed164d8443dbd474ce35934a3235c0337943..04d8527c7a20a3cbfbf73d4b357d0e2f8c7000da 100644
--- a/content/public/child/child_thread.h
+++ b/content/public/child/child_thread.h
@@ -6,6 +6,7 @@
 #define CONTENT_PUBLIC_CHILD_CHILD_THREAD_H_
 
 #include "content/common/content_export.h"
+#include "ipc/attachment_broker.h"
 #include "ipc/ipc_sender.h"
 
 #if defined(OS_WIN)
@@ -14,7 +15,11 @@
 
 namespace content {
 
-class CONTENT_EXPORT ChildThread : public IPC::Sender {
+// An abstract base class that contains logic shared between most child
+// processes of the embedder.
+class CONTENT_EXPORT ChildThread
+    : public IPC::Sender,
+      virtual public IPC::SupportsAttachmentBrokering {
  public:
   // Returns the one child thread for this process.  Note that this can only be
   // accessed when running on the child thread itself.