Adding a new message type to the Mojo channel.

mojo/edk/system/node_channel.cc

Index: mojo/edk/system/node_channel.cc
diff --git a/mojo/edk/system/node_channel.cc b/mojo/edk/system/node_channel.cc
index da9e0dbf25c3bcd53413b119e566e11e28365d0c..91a69c3b9db27361c00fba41806f38ab9cac9d5f 100644
--- a/mojo/edk/system/node_channel.cc
+++ b/mojo/edk/system/node_channel.cc
@@ -55,8 +55,8 @@ struct Header {
   uint32_t padding;
 };
 
-static_assert(sizeof(Header) % kChannelMessageAlignment == 0,
-    "Invalid header size.");
+static_assert(IsAlignedForChannelMessage(sizeof(Header)),
+              "Invalid header size.");
 
 struct AcceptChildData {
   ports::NodeName parent_name;