Mojo C++ bindings: support disconnect with a reason.

mojo/public/interfaces/bindings/interface_control_messages.mojom

Index: mojo/public/interfaces/bindings/interface_control_messages.mojom
diff --git a/mojo/public/interfaces/bindings/interface_control_messages.mojom b/mojo/public/interfaces/bindings/interface_control_messages.mojom
index 42b6297d05157c36a9eee90a3af7ff0f5db7c676..39d7bde9b0b86ed28cac246d8e999e6d64b0ea02 100644
--- a/mojo/public/interfaces/bindings/interface_control_messages.mojom
+++ b/mojo/public/interfaces/bindings/interface_control_messages.mojom
@@ -5,9 +5,8 @@
 [JavaPackage="org.chromium.mojo.bindings.interfacecontrol"]
 module mojo.interface_control;
 
-// For each user-defined interface, some control functions are provided at the
-// same end of the message pipe as the user-defined interface, providing
-// information about the user-defined interface.
+// For each user-defined interface, some control functions are provided by the
+// interface endpoints at both sides.
 
 ////////////////////////////////////////////////////////////////////////////////
 // Run@0xFFFFFFFF(RunInput input) => (RunOutput? output);
@@ -34,12 +33,14 @@ union RunOutput {
 };
 
 // Queries the max supported version of the user-defined interface.
+// Sent by the interface client side.
 struct QueryVersion {
 };
 struct QueryVersionResult {
   uint32 version;
 };
 
+// Sent by either side of the interface.
 struct FlushForTesting {
 };
 
@@ -56,10 +57,20 @@ struct RunOrClosePipeMessageParams {
 };
 union RunOrClosePipeInput {
   RequireVersion require_version;
+  SendDisconnectReason send_disconnect_reason;
 };
 
 // If the specified version of the user-defined interface is not supported, the
 // function fails and the pipe is closed.
+// Sent by the interface client side.
 struct RequireVersion {
   uint32 version;
 };
+
+// A user-defined reason about why the interface is disconnected. The sender
+// usually send this message and immediately disconnect the interface.
+// Sent by either side of the interface.
+struct SendDisconnectReason {
+  uint32 custom_reason;
+  string description;
+};