Add interfaces for most major Blimp net components.

blimp/engine/net/BUILD.gn

Index: blimp/engine/net/BUILD.gn
diff --git a/components/data_use_measurement/core/BUILD.gn b/blimp/engine/net/BUILD.gn
similarity index 65%
copy from components/data_use_measurement/core/BUILD.gn
copy to blimp/engine/net/BUILD.gn
index c9de08dac0089a8a1077e94203fcbbf02a161c4d..a94a8006025f35b4d7d7f9f68838ff15e36e9c86 100644
--- a/components/data_use_measurement/core/BUILD.gn
+++ b/blimp/engine/net/BUILD.gn
@@ -2,13 +2,15 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("core") {
+source_set("net") {

[Wez, 2015/11/12 00:12:53]

Re the directory structure; it seems overkill to have client/net and engine/net
- could we just have blimp/net and prefix the classes in there with client_ or
engine_ as appropriate

   sources = [
-    "data_use_user_data.cc",
-    "data_use_user_data.h",
+    "engine_connection_manager.cc",
+    "engine_connection_manager.h",
   ]
+
   deps = [
     "//base",
+    "//blimp/net:blimp_net",
     "//net",
   ]
 }