Add a basic UI to the Android Blimp client.

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 fdc1c89919522324905a8b75648a79e5c5a9d220..f01654b28096147a8899e3d78c52dab1171bd61e 100644
--- a/blimp/common/proto/control.proto
+++ b/blimp/common/proto/control.proto
@@ -8,21 +8,11 @@ syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
-message LoadUrlMessage {
-  optional string url = 1;
-}
-
 message ControlMessage {
   enum Type {
     // Client <=> Server types.
     CREATE_TAB = 1;
     CLOSE_TAB = 2;
-    LOAD_URL = 3;
-
-    // Server => Client types.
-    // Client => Server types.
   }
   optional Type type = 1;
-
-  optional LoadUrlMessage load_url = 1000;
 }