Making the Mojo Channel Messages legacy mode dynamic.

mojo/edk/embedder/embedder.cc

Index: mojo/edk/embedder/embedder.cc
diff --git a/mojo/edk/embedder/embedder.cc b/mojo/edk/embedder/embedder.cc
index 0fdda5cd1c72bbf512f56ba07ab5f681b5f43241..ec069fa72f83088393168485a72d05a0c01d02ee 100644
--- a/mojo/edk/embedder/embedder.cc
+++ b/mojo/edk/embedder/embedder.cc
@@ -18,6 +18,7 @@
 #include "mojo/edk/embedder/embedder_internal.h"
 #include "mojo/edk/embedder/entrypoints.h"
 #include "mojo/edk/embedder/platform_channel_pair.h"
+#include "mojo/edk/system/channel.h"
 #include "mojo/edk/system/core.h"
 #include "mojo/edk/system/node_controller.h"
 
@@ -74,7 +75,9 @@ void Init() {
   MojoSystemThunks thunks = MakeSystemThunks();
   size_t expected_size = MojoEmbedderSetSystemThunks(&thunks);
   DCHECK_EQ(expected_size, sizeof(thunks));
-
+#if defined(MOJO_EDK_LEGACY_PROTOCOL)
+  SetUseLegacyTransportProtocol(true);
+#endif
   internal::g_core = new Core();
 }
 
@@ -82,6 +85,10 @@ void SetDefaultProcessErrorCallback(const ProcessErrorCallback& callback) {
   internal::g_core->SetDefaultProcessErrorCallback(callback);
 }
 
+void SetUseLegacyTransportProtocol(bool use_legacy_protocol) {
+  Channel::Message::SetUseLegacyTransportProtocol(use_legacy_protocol);
+}
+
 MojoResult CreatePlatformHandleWrapper(
     ScopedPlatformHandle platform_handle,
     MojoHandle* platform_handle_wrapper_handle) {