url: add inspect function to TupleOrigin

This adds a simple inspect function the the TupleOrigin class.
This adds tests for the newly added inspect function in the TupleOrigin
class.

PR-URL: nodejs#10039
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

lib/internal/url.js

@@ -69,6 +69,15 @@ class TupleOrigin {
       result += `:${this.port}`;
     return result;
   }
+
+  inspect() {
+    return `TupleOrigin {
+      scheme: ${this.scheme},
+      host: ${this.host},
+      port: ${this.port},
+      domain: ${this.domain}
+    }`;
+  }
 }
 
 class URL {

test/parallel/test-util-inspect-tuple-origin.js

@@ -0,0 +1,37 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+const inspect = require('util').inspect;
+const URL = require('url').URL;
+
+assert.strictEqual(
+    inspect(URL.originFor('http://test.com:8000')),
+    `TupleOrigin {
+      scheme: http,
+      host: test.com,
+      port: 8000,
+      domain: null
+    }`
+  );
+
+assert.strictEqual(
+    inspect(URL.originFor('http://test.com')),
+    `TupleOrigin {
+      scheme: http,
+      host: test.com,
+      port: undefined,
+      domain: null
+    }`
+  );
+
+
+assert.strictEqual(
+    inspect(URL.originFor('https://test.com')),
+    `TupleOrigin {
+      scheme: https,
+      host: test.com,
+      port: undefined,
+      domain: null
+    }`
+  );