Use unions for interface control messages.

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 2143c06cce5c64a015599e3fb040628964637ded..8f88bf66201699a51c44759b1b38924bfac5c2e9 100644
--- a/mojo/public/interfaces/bindings/interface_control_messages.mojom
+++ b/mojo/public/interfaces/bindings/interface_control_messages.mojom
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 [JavaPackage="org.chromium.mojo.bindings"]

[yzshen1, 2016/08/25 21:08:57]

nit: do you think it is better to change this name to something more consistent?

The pipe_control_messages.mojom is using org.chromium.mojo.bindings.pipecontrol

[Sam McNally, 2016/08/25 21:47:50]

Done.

-module mojo;
+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
@@ -15,38 +15,20 @@ module mojo;
 // This control function runs the input command. If the command is not
 // supported, |output| is set to null; otherwise |output| stores the result,
 // whose type depends on the input.
-//
-// TODO(yzshen): Once union support is ready, switch the following definition
-// to:
-// struct RunMessageParams {
-//   RunInput input;
-// };
-// union RunInput {
-//   QueryVersion query_version;
-// };
-//
-// struct RunResponseMessageParams {
-//   RunOutput? output;
-// };
-// union RunOutput {
-//   QueryVersionResult query_version_result;
-// };
 
 const uint32 kRunMessageId = 0xFFFFFFFF;
 
 struct RunMessageParams {
-  // The reserved fields make the layout compatible with the RunInput union
-  // described above.
-  uint32 reserved0;  // Must be set to 16.
-  uint32 reserved1;  // Must be set to 0;
+  RunInput input;
+};
+union RunInput {
   QueryVersion query_version;
 };
 
 struct RunResponseMessageParams {
-  // The reserved fields make the layout compatible with the RunOutput union
-  // described above.
-  uint32 reserved0;  // Must be set to 16.
-  uint32 reserved1;  // Must be set to 0.
+  RunOutput? output;
+};
+union RunOutput {
   QueryVersionResult query_version_result;
 };
 
@@ -62,23 +44,13 @@ struct QueryVersionResult {
 //
 // This control function runs the input command. If the operation fails or the
 // command is not supported, the message pipe is closed.
-//
-// TODO(yzshen): Once union support is ready, switch the following definition
-// to:
-// struct RunOrClosePipeMessageParams {
-//   RunOrClosePipeInput input;
-// };
-// union RunOrClosePipeInput {
-//   RequireVersion require_version;
-// };
 
 const uint32 kRunOrClosePipeMessageId = 0xFFFFFFFE;
 
 struct RunOrClosePipeMessageParams {
-  // The reserved fields make the layout compatible with the RunOrClosePipeInput
-  // union described above.
-  uint32 reserved0;  // Must be set to 16.
-  uint32 reserved1;  // Must be set to 0.
+  RunOrClosePipeInput input;
+};
+union RunOrClosePipeInput {
   RequireVersion require_version;
 };