Add descriptions with examples to run-blink-* scripts.

third_party/WebKit/Tools/Scripts/run-blink-wptserve

Index: third_party/WebKit/Tools/Scripts/run-blink-wptserve
diff --git a/third_party/WebKit/Tools/Scripts/run-blink-wptserve b/third_party/WebKit/Tools/Scripts/run-blink-wptserve
index f94e7c850aac2e8d5f36d944defe77da18bbc98b..f13952e28306431054fd6a7939f80111cdb02ec8 100755
--- a/third_party/WebKit/Tools/Scripts/run-blink-wptserve
+++ b/third_party/WebKit/Tools/Scripts/run-blink-wptserve
@@ -3,13 +3,19 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-# Runs an instance of wptserve to allow manual testing of the imported Web
-# Platform Tests. The main HTTP server is run on 8001, while the main HTTPS
-# server is run on 8444.
+"""Runs an instance of wptserve to allow manual testing of web-platform-tests.
+
+The main HTTP server is run on 8001, while the main HTTPS server is run on 8444.
+
+URL paths are relative to the web-platform-tests root, e.g. the test:
+    LayoutTests/external/wpt/referrer-policy/origin/http-rp/same-origin/http-http/img-tag/generic.no-redirect.http.html
+Could be tried by running this scrip then navigating to:
+    http://localhost:8001/referrer-policy/origin/http-rp/same-origin/http-http/img-tag/generic.no-redirect.http.html
+"""
 
 import webkitpy.common.version_check
 
 from webkitpy.layout_tests.servers import cli_wrapper
 from webkitpy.layout_tests.servers import wptserve
 
-cli_wrapper.main(wptserve.WPTServe)
+cli_wrapper.main(wptserve.WPTServe, description=__doc__)