[mojo] Add CreateSharedBuffer method to Broker.

mojo/edk/system/broker_messages.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_EDK_SYSTEM_BROKER_MESSAGES_H_
 #define MOJO_EDK_SYSTEM_BROKER_MESSAGES_H_
 
 #include <stdint.h>
 
 #include "base/compiler_specific.h"
 #include "base/process/process_handle.h"
 
 namespace mojo {
 namespace edk {
 
 // This header defines the message format between ChildBroker and
 // ChildBrokerHost.
 
 #if defined(OS_WIN)
 // Windows only messages needed because sandboxed child processes need the
 // parent's help. They are sent synchronously from child to parent and each have
 // a response. They are sent over a raw pipe.
 enum WindowsSandboxMessages {

[jam, 2016/01/06 02:58:16]

nit: lets share the enum class type and just have ifdef around the IDs. that
would simplify things a little (i.e. BrokerMessage can use the same type)

[Eliot Courtney, 2016/01/07 02:26:08]

Done.

   // The reply is two HANDLEs.
   CREATE_PLATFORM_CHANNEL_PAIR = 0,
   // The reply is tokens of the same count of passed in handles.
   HANDLE_TO_TOKEN,
   // The reply is handles of the same count of passed in tokens.
   TOKEN_TO_HANDLE,
 };
 
+#else
+// Sandbox processes need the parent's help to create shared buffers.
+enum PosixSandboxMessages {
+  // The reply is a PlatformHandle.
+  CREATE_SHARED_BUFFER = 0
+};
+#endif
+
 // Definitions of the raw bytes sent in messages.
 
 struct BrokerMessage {
   uint32_t size;
+#if defined(OS_WIN)
   WindowsSandboxMessages id;
   // Data, if any, follows.
   union {
     HANDLE handles[1];  // If HANDLE_TO_TOKEN.
     uint64_t tokens[1];  // If TOKEN_TO_HANDLE.
   };
+#else
+  PosixSandboxMessages id;
+
+  uint32_t num_bytes;  // Size of the shared buffer to create.
+#endif
 };
 
-const int kBrokerMessageHeaderSize =
-  sizeof(uint32_t) + sizeof(WindowsSandboxMessages);
-
+const int kBrokerMessageHeaderSize = sizeof(uint32_t) +
+#if defined(OS_WIN)
+                                     sizeof(WindowsSandboxMessages);
+#else
+                                     sizeof(PosixSandboxMessages);
 #endif
 
 // Route id used for messages between ChildBroker and ChildBrokerHost.
 const uint64_t kBrokerRouteId = 1;
 
 // Multiplexing related messages. They are all asynchronous messages.
 // They are sent over RawChannel.
 enum MultiplexMessages {
   // Messages from child to parent.
   CONNECT_MESSAGE_PIPE = 0,
@@ skipping 19 matching lines @@
 struct PeerPipeConnectedMessage {
   MultiplexMessages type;  // PEER_PIPE_CONNECTED
   uint64_t pipe_id;
   base::ProcessId process_id;
 };
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_BROKER_MESSAGES_H_