Add glue between the client and engine for Blimp

blimp/common/proto/control.proto

Index: blimp/common/proto/control.proto
diff --git a/blimp/common/proto/control.proto b/blimp/common/proto/control.proto
index f01654b28096147a8899e3d78c52dab1171bd61e..08a7e77011d896e1c390489eac7c8861c7aa6b3c 100644
--- a/blimp/common/proto/control.proto
+++ b/blimp/common/proto/control.proto
@@ -8,11 +8,23 @@ syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
+import "size.proto";
+
+package blimp;
+
 message ControlMessage {
   enum Type {
     // Client <=> Server types.
     CREATE_TAB = 1;
     CLOSE_TAB = 2;
+
+    // Client => Server types.
+    SIZE = 3;
   }
+
   optional Type type = 1;
+
+  // Feature-specific messages follow.
+  // Only one of these fields may be set per ControlMessage.
+  optional SizeMessage resize = 1000;
 }