[mojo] Add CreateSharedBuffer method to Broker.

mojo/edk/system/child_broker.h

Index: mojo/edk/system/child_broker.h
diff --git a/mojo/edk/system/child_broker.h b/mojo/edk/system/child_broker.h
index 49bd05fb230456943b464080f9b7bb5dd9096934..7b513b1d9709c1d042507e5e6ca1c8135e8004d4 100644
--- a/mojo/edk/system/child_broker.h
+++ b/mojo/edk/system/child_broker.h
@@ -46,7 +46,11 @@ class MOJO_SYSTEM_IMPL_EXPORT ChildBroker
   void TokenToHandle(const uint64_t* tokens,
                      size_t count,
                      PlatformHandle* handles) override;
+#else
+  scoped_refptr<PlatformSharedBuffer> CreateSharedBuffer(
+      size_t num_bytes) override;
 #endif
+
   void ConnectMessagePipe(uint64_t pipe_id,
                           MessagePipeDispatcher* message_pipe) override;
   void CloseMessagePipe(uint64_t pipe_id,
@@ -87,6 +91,13 @@ class MOJO_SYSTEM_IMPL_EXPORT ChildBroker
   void CreatePlatformChannelPairNoLock(ScopedPlatformHandle* server,
                                        ScopedPlatformHandle* client);
 
+#else
+  // Will fully write |message|, then read back some number of handles. Returns
+  // false if the write or read failed, or if there were no handles received.
+  bool WriteAndReadHandles(BrokerMessage* message,
+                           std::deque<PlatformHandle>* handles);
+#endif
+
   // Guards access to |parent_sync_channel_|.
   // We use LockImpl instead of Lock because the latter adds thread checking
   // that we don't want (since we lock in the constructor and unlock on another
@@ -97,7 +108,6 @@ class MOJO_SYSTEM_IMPL_EXPORT ChildBroker
   // instead of bindings or RawChannel because we need to send synchronous
   // messages with replies from any thread.
   ScopedPlatformHandle parent_sync_channel_;
-#endif
 
   // RawChannel used for asynchronous communication to and from the parent
   // process. Since these messages are bidirectional, we can't use