Adds associated interface support to IPC::Channel

ipc/ipc_channel.h

Index: ipc/ipc_channel.h
diff --git a/ipc/ipc_channel.h b/ipc/ipc_channel.h
index 09baf6cf14044ecc32315789b9ee84915bea36b6..1fc9c6c531bbd3d43440be292f169a7b38bc54d6 100644
--- a/ipc/ipc_channel.h
+++ b/ipc/ipc_channel.h
@@ -18,6 +18,10 @@
 #include "ipc/ipc_channel_handle.h"
 #include "ipc/ipc_endpoint.h"
 #include "ipc/ipc_message.h"
+#include "mojo/public/cpp/bindings/associated_group.h"
+#include "mojo/public/cpp/bindings/associated_interface_ptr.h"
+#include "mojo/public/cpp/bindings/associated_interface_request.h"
+#include "mojo/public/cpp/bindings/scoped_interface_endpoint_handle.h"
 
 #if defined(OS_POSIX)
 #include <sys/types.h>
@@ -93,6 +97,62 @@ class IPC_EXPORT Channel : public Endpoint {
     CLOSE_FD_MESSAGE_TYPE = HELLO_MESSAGE_TYPE - 1
   };
 
+  // Helper interface a Channel may implement to expose support for associated
+  // Mojo interfaces.
+  class IPC_EXPORT AssociatedInterfaceSupport {
+   public:
+    using GenericAssociatedInterfaceFactory =
+        base::Callback<void(mojo::ScopedInterfaceEndpointHandle)>;
+
+    virtual ~AssociatedInterfaceSupport() {}
+
+    // Accesses the AssociatedGroup used to associate new interface endpoints
+    // with this Channel.
+    virtual mojo::AssociatedGroup* GetAssociatedGroup() = 0;
+
+    // Adds an interface factory to this channel for interface |name|.
+    virtual void AddGenericAssociatedInterface(
+        const std::string& name,
+        const GenericAssociatedInterfaceFactory& factory) = 0;
+
+    // Requests an associated interface from the remote endpoint.
+    virtual void GetGenericRemoteAssociatedInterface(
+        const std::string& name,
+        mojo::ScopedInterfaceEndpointHandle handle) = 0;
+
+    // Template helper to add an interface factory to this channel.
+    template <typename Interface>
+    using AssociatedInterfaceFactory =
+        base::Callback<void(mojo::AssociatedInterfaceRequest<Interface>)>;
+    template <typename Interface>
+    void AddAssociatedInterface(
+        const AssociatedInterfaceFactory<Interface>& factory) {
+      AddGenericAssociatedInterface(
+          Interface::Name_,
+          base::Bind(&BindAssociatedInterfaceRequest<Interface>, factory));
+    }
+
+    // Template helper to request a remote associated interface.
+    template <typename Interface>
+    void GetRemoteAssociatedInterface(
+        mojo::AssociatedInterfacePtr<Interface>* proxy) {
+      mojo::AssociatedInterfaceRequest<Interface> request =
+          mojo::GetProxy(proxy, GetAssociatedGroup());
+      GetGenericRemoteAssociatedInterface(
+          Interface::Name_, request.PassHandle());
+    }
+
+   private:
+    template <typename Interface>
+    static void BindAssociatedInterfaceRequest(
+        const AssociatedInterfaceFactory<Interface>& factory,
+        mojo::ScopedInterfaceEndpointHandle handle) {
+      mojo::AssociatedInterfaceRequest<Interface> request;
+      request.Bind(std::move(handle));
+      factory.Run(std::move(request));
+    }
+  };
+
   // The maximum message size in bytes. Attempting to receive a message of this
   // size or bigger results in a channel error.
   static const size_t kMaximumMessageSize = 128 * 1024 * 1024;
@@ -181,6 +241,11 @@ class IPC_EXPORT Channel : public Endpoint {
   // Get its own process id. This value is told to the peer.
   virtual base::ProcessId GetSelfPID() const = 0;
 
+  // Gets a helper for associating Mojo interfaces with this Channel.
+  //
+  // NOTE: Not all implementations support this.
+  virtual AssociatedInterfaceSupport* GetAssociatedInterfaceSupport();
+
   // Overridden from ipc::Sender.
   // Send a message over the Channel to the listener on the other end.
   //