[mojo-edk] Add explicit message object APIs

mojo/edk/system/core_test_base.cc

Index: mojo/edk/system/core_test_base.cc
diff --git a/mojo/edk/system/core_test_base.cc b/mojo/edk/system/core_test_base.cc
index 635501aa2c7638dce467e819d80b4f9b2e129a1f..e98a55d2ad154b512cb6799e4cec32af70b4a70c 100644
--- a/mojo/edk/system/core_test_base.cc
+++ b/mojo/edk/system/core_test_base.cc
@@ -16,6 +16,7 @@
 #include "mojo/edk/system/configuration.h"
 #include "mojo/edk/system/core.h"
 #include "mojo/edk/system/dispatcher.h"
+#include "mojo/edk/system/message_for_transit.h"
 
 namespace mojo {
 namespace edk {
@@ -41,27 +42,25 @@ class MockDispatcher : public Dispatcher {
   }
 
   MojoResult WriteMessage(
-      const void* bytes,
-      uint32_t num_bytes,
-      const DispatcherInTransit* dispatchers,
-      uint32_t num_dispatchers,
+      std::unique_ptr<MessageForTransit> message,
       MojoWriteMessageFlags /*flags*/) override {
     info_->IncrementWriteMessageCallCount();
 
-    if (num_bytes > GetConfiguration().max_message_num_bytes)
+    if (message->num_bytes() > GetConfiguration().max_message_num_bytes)
       return MOJO_RESULT_RESOURCE_EXHAUSTED;
 
-    if (dispatchers)
+    if (message->num_handles())
       return MOJO_RESULT_UNIMPLEMENTED;
 
     return MOJO_RESULT_OK;
   }
 
-  MojoResult ReadMessage(void* bytes,
+  MojoResult ReadMessage(std::unique_ptr<MessageForTransit>* message,
                          uint32_t* num_bytes,
                          MojoHandle* handle,
                          uint32_t* num_handles,
-                         MojoReadMessageFlags /*flags*/) override {
+                         MojoReadMessageFlags /*flags*/,
+                         bool ignore_num_bytes) override {
     info_->IncrementReadMessageCallCount();
 
     if (num_handles)