Update contents to use attachment broker.

content/public/common/child_process_host.h

Index: content/public/common/child_process_host.h
diff --git a/content/public/common/child_process_host.h b/content/public/common/child_process_host.h
index 3794c21eb0d15446b1f1c1aacc44eff34a55c95e..0d4815a21dde3280b119e80e31ca75d2e92b2bbf 100644
--- a/content/public/common/child_process_host.h
+++ b/content/public/common/child_process_host.h
@@ -8,6 +8,7 @@
 #include "base/files/scoped_file.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
+#include "ipc/attachment_broker_privileged.h"

[erikchen, 2015/07/30 17:24:40]

Some consumers want an IPC::AttachmentBroker, while others want
IPC::AttachmentBrokerPrivileged. Adding this include exposes the class
hierarchy, which means that consumers can implicitly downcast
AttachmentBrokerPrivileged to AttachmentBroker without having to explicitly
include this header. 

 #include "ipc/ipc_channel_proxy.h"
 
 namespace base {
@@ -15,7 +16,6 @@ class FilePath;
 }
 
 namespace IPC {
-class AttachmentBroker;
 class MessageFilter;
 }
 
@@ -91,7 +91,7 @@ class CONTENT_EXPORT ChildProcessHost : public IPC::Sender {
 
   // Returns an AttachmentBroker used to broker attachments of IPC messages to
   // child processes.
-  static IPC::AttachmentBroker* GetAttachmentBroker();
+  static IPC::AttachmentBrokerPrivileged* GetAttachmentBroker();
 
   // Send the shutdown message to the child process.
   // Does not check with the delegate's CanShutdown.