playground/client: Use backend proxy.

Backend is now at <proto>://<host>/api by default.

Change-Id: I6ced906a00fdc7f8b10156a3d6c12e890af1673a
diff --git a/client/README.md b/client/README.md
index c6e9f4c..84d9816 100644
--- a/client/README.md
+++ b/client/README.md
@@ -31,6 +31,9 @@
 
     make start
 
+The client running on localhost needs to have the backend address configured via the
+`pgaddr=` query parameter.
+
 As of dec-2014, the playground doc is [here][playground-doc].
 
 # Deploy
diff --git a/client/src/javascript/playground.js b/client/src/javascript/playground.js
index 8223fcf..6991081 100644
--- a/client/src/javascript/playground.js
+++ b/client/src/javascript/playground.js
@@ -150,10 +150,8 @@
       pgaddr = '';
     }
   }
-  // TODO(ivanpi): Enable HTTPS and remove port when proxy is set up.
-  var origin = 'http://' + window.location.hostname + ':8181';
-  //var origin = window.location.protocol + '//' + window.location.host;
-  var defaddr = origin.replace('playground', 'pgapi');
+  var origin = window.location.protocol + '//' + window.location.host;
+  var defaddr = origin + '/api';
   console.log('Using default backend', defaddr);
   return defaddr;
 };
diff --git a/go/src/playground/README.md b/go/src/playground/README.md
index 6fd7155..75348cc 100644
--- a/go/src/playground/README.md
+++ b/go/src/playground/README.md
@@ -64,7 +64,8 @@
 The server should now be running at http://localhost:8181 and responding to
 compile requests at http://localhost:8181/compile.
 
-Add `?pgaddr=//localhost:8181` to any playground page to make the client talk
-to your server. Add `?debug=1` to see debug info from the builder.
+Add `?pgaddr=http://localhost:8181` to any playground page on localhost to
+make the client talk to your server. Add `?debug=1` to see debug info from
+the builder.
 
 TODO: storage