Blimp: Add BlobChannel Helium messages and delegate impls.

blimp/common/create_blimp_message.cc

Index: blimp/common/create_blimp_message.cc
diff --git a/blimp/common/create_blimp_message.cc b/blimp/common/create_blimp_message.cc
index 460560c6851c6513ff1ebf32150a5e3de6f8ebd6..a3af17d6c8baf4be6ef8b3e887a50f0474caea00 100644
--- a/blimp/common/create_blimp_message.cc
+++ b/blimp/common/create_blimp_message.cc
@@ -8,6 +8,7 @@
 
 #include "base/logging.h"
 #include "blimp/common/proto/blimp_message.pb.h"
+#include "blimp/common/proto/blob_channel.pb.h"
 #include "blimp/common/proto/compositor.pb.h"
 #include "blimp/common/proto/input.pb.h"
 #include "blimp/common/proto/render_widget.pb.h"
@@ -80,6 +81,13 @@ std::unique_ptr<BlimpMessage> CreateBlimpMessage(
   return output;
 }
 
+std::unique_ptr<BlimpMessage> CreateBlimpMessage(
+    BlobChannelMessage** blob_channel_message) {
+  std::unique_ptr<BlimpMessage> output(new BlimpMessage);
+  *blob_channel_message = output->mutable_blob_channel();
+  return output;
+}
+
 std::unique_ptr<BlimpMessage> CreateStartConnectionMessage(
     const std::string& client_token,
     int protocol_version) {