Added network components for blimp text input feature

blimp/common/create_blimp_message.cc

Index: blimp/common/create_blimp_message.cc
diff --git a/blimp/common/create_blimp_message.cc b/blimp/common/create_blimp_message.cc
index 09e6dea0cb7fa70a0fe3aa0c2f7efebbce913f02..ddb28dc9592fefed54815e8e330584a3a965957b 100644
--- a/blimp/common/create_blimp_message.cc
+++ b/blimp/common/create_blimp_message.cc
@@ -53,6 +53,16 @@ scoped_ptr<BlimpMessage> CreateBlimpMessage(
   return output;
 }
 
+scoped_ptr<BlimpMessage> CreateBlimpMessage(ImeMessage** ime_message,
+                                            int target_tab_id) {
+  DCHECK(ime_message);

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

nit: Why do we DCHECK the out-parameter here & in the other CreateBlimpMessage
impls? We de-reference it later in the same function, to assign to it, so DCHECK
is redundant.

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

Pingy.

[shaktisahu, 2016/03/22 23:45:42]

Since ime_message is a pointer to pointer, shouldn't we do a null check before
de-referencing its value?

[Wez, 2016/03/23 00:10:53]

DCHECK makes sense where you are given a pointer that you are not immediately
going to dereference - then rather than crashing when you dereference it and not
knowing why you got a null pointer, you will get a nice DCHECK at the point
where the caller passed you something invalid.

In this case you are dereferencing it on line #62 - if it's null then the app
will crash, which is all that DCHECK will do - so all the DCHECK is doing is
moving the crash earlier in this function, which isn't useful.

[shaktisahu, 2016/03/23 01:44:13]

I think DCHECK makes it easier for me to debug in the event of a crash. But if
you feel strongly about it, I will remove this.

[Wez, 2016/03/23 23:21:25]

How does it make it easier?

+  scoped_ptr<BlimpMessage> output(new BlimpMessage);
+  output->set_type(BlimpMessage::IME);
+  output->set_target_tab_id(target_tab_id);
+  *ime_message = output->mutable_ime();
+  return output;
+}
+
 scoped_ptr<BlimpMessage> CreateBlimpMessage(
     RenderWidgetMessage** render_widget_message,
     int target_tab_id) {