[remoting android] Add and build host code.

remoting/host/BUILD.gn

Index: remoting/host/BUILD.gn
diff --git a/remoting/host/BUILD.gn b/remoting/host/BUILD.gn
index 93fdf430246e23b45cf9eb597238fc16a383216b..a8d05f8d912ad55241bd7c654b53e0fc18c0e89b 100644
--- a/remoting/host/BUILD.gn
+++ b/remoting/host/BUILD.gn
@@ -194,6 +194,13 @@ if (is_mac) {  # TODO(GYP) Mac build of remoting host.
     if (enable_webrtc) {
       deps += [ "//third_party/webrtc/modules/desktop_capture" ]
     }
+
+    if (is_android) {
+      sources -= [
+        "single_window_desktop_environment.cc",
+        "single_window_desktop_environment.h",
+      ]
+    }
   }
 
   source_set("test_support") {