Added network components for blimp text input feature

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 db73e03c5a1a29863793fe70a85c022d516e76ba..4618a4fcabeddf7e1a7fecf025568cdf7d0295ab 100644
--- a/blimp/common/proto/blimp_message.proto
+++ b/blimp/common/proto/blimp_message.proto
@@ -24,6 +24,7 @@ syntax = "proto2";
 option optimize_for = LITE_RUNTIME;
 
 import "compositor.proto";
+import "ime.proto";
 import "input.proto";
 import "navigation.proto";
 import "render_widget.proto";
@@ -41,6 +42,7 @@ message BlimpMessage {
     INPUT = 4;
     COMPOSITOR = 5;
     PROTOCOL_CONTROL = 6;
+    IME = 7;

[Wez, 2016/03/18 20:51:28]

What is the rationale for adding a top-level ImeMessage rather than folding
these messages under INPUT?

If we keep them separate then can we call it TEXT_INPUT/TextInputMessage?
Without any surrounding context, IME's meaning is not immediately obvious!

[shaktisahu, 2016/03/22 19:44:20]

IME message is both way (client<-->server) whereas INPUT messages are one way. I
can change the name. There are few names I have used so far :
BlimpMessage::IME/ImeMessage, ImeFeature, WebInputBox. Please suggest what seems
more appropriate.

[Wez, 2016/03/22 21:43:38]

Let's stick w/ this for now & revisit naming if it proves troublesome.

   }
 
   // Sequence number of this message, used for message acknowledgement.
@@ -74,5 +76,6 @@ message BlimpMessage {
   optional InputMessage input = 1003;
   optional CompositorMessage compositor = 1004;
   optional ProtocolControlMessage protocol_control = 1005;
+  optional ImeMessage ime = 1006;
 }