Escape the URL passed to RegEx (web-platform-tests#193)

testharness.js

@@ -2464,7 +2464,9 @@ policies and contribution forms [3].
 
         // Create a pattern to match stack frames originating within testharness.js.  These include the
         // script URL, followed by the line/col (e.g., '/resources/testharness.js:120:21').
-        var re = new RegExp((get_script_url() || "\\btestharness.js") + ":\\d+:\\d+");
+        // Escape the URL per http://stackoverflow.com/questions/3561493/is-there-a-regexp-escape-function-in-javascript
+        // in case it contains RegExp characters.
+        var re = new RegExp((get_script_url().replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&') || "\\btestharness.js") + ":\\d+:\\d+");
 
         // Some browsers include a preamble that specifies the type of the error object.  Skip this by
         // advancing until we find the first stack frame originating from testharness.js.