[Blimp Net] Add EngineAuthHandler.

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 5841cd802d6b17603e79518e095076d2b57180f1..3bf22f848eafd6402516a41227238b63de22d29b 100644
--- a/blimp/common/proto/blimp_message.proto
+++ b/blimp/common/proto/blimp_message.proto
@@ -28,6 +28,7 @@ import "compositor.proto";
 import "input.proto";
 import "navigation.proto";
 import "render_widget.proto";
+import "protocol_control.proto";
 
 package blimp;
 
@@ -39,6 +40,7 @@ message BlimpMessage {
     RENDER_WIDGET = 3;
     INPUT = 4;
     COMPOSITOR = 5;
+    PROTOCOL_CONTROL = 6;
   }
 
   // Sequence number of this message, used for message acknowledgement.
@@ -70,5 +72,6 @@ message BlimpMessage {
   optional RenderWidgetMessage render_widget = 1002;
   optional InputMessage input = 1003;
   optional CompositorMessage compositor = 1004;
+  optional ProtocolControlMessage protocol_control = 1005;
 }