Blimp: define HeliumTransport/HeliumStream interfaces.

blimp/net/BUILD.gn

Index: blimp/net/BUILD.gn
diff --git a/blimp/net/BUILD.gn b/blimp/net/BUILD.gn
index 9c3488256c37fc6b164cb2d4c95c9f9d7da0e891..81c372f9af3f6446e17f62097d0d2aa3c7f91838 100644
--- a/blimp/net/BUILD.gn
+++ b/blimp/net/BUILD.gn
@@ -77,6 +77,7 @@ component("net") {
   defines = [ "BLIMP_NET_IMPLEMENTATION=1" ]
 
   deps = [
+    ":helium",
     "//base",
     "//blimp/common",
     "//net",
@@ -90,6 +91,14 @@ component("net") {
   ]
 }
 
+source_set("helium") {
+  sources = [
+    "helium/helium_stream.cc",
+    "helium/helium_stream.h",
+    "helium/helium_transport.h",
+  ]
+}
+
 source_set("test_support") {
   testonly = true