Blimp: Add BlobChannel Helium messages and delegate impls.

blimp/common/proto/blimp_message.proto

Index: blimp/common/proto/blimp_message.proto
diff --git a/blimp/common/proto/blimp_message.proto b/blimp/common/proto/blimp_message.proto
index 5a8ad614d2d23cc9b20a8dde763a2cedb3f4d251..484199343a91ac832e848e8921cbdcca3ddbaa88 100644
--- a/blimp/common/proto/blimp_message.proto
+++ b/blimp/common/proto/blimp_message.proto
@@ -23,6 +23,7 @@ syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
+import "blob_channel.proto";
 import "compositor.proto";
 import "ime.proto";
 import "input.proto";
@@ -45,6 +46,7 @@ message BlimpMessage {
     PROTOCOL_CONTROL = 6;
     IME = 7;
     SETTINGS = 8;
+    BLOB_CHANNEL = 9;
   }
 
   // Sequence number of this message, used for message acknowledgement.
@@ -80,5 +82,6 @@ message BlimpMessage {
   optional ProtocolControlMessage protocol_control = 1005;
   optional ImeMessage ime = 1006;
   optional SettingsMessage settings = 1007;
+  optional BlobChannelMessage blob_channel = 1008;
 }