allow setBreakpoint(line)

lib/_debugger.js

@@ -1304,6 +1304,12 @@ Interface.prototype.setBreakpoint = function(script, line,
     line = this.client.currentSourceLine + 1;
   }
 
+  // setBreakpoint(line-number) should insert breakpoint in current script
+  if (line === undefined && typeof script === 'number') {
+    line = script;
+    script = this.client.currentScript;
+  }
+
   if (/\(\)$/.test(script)) {
     // setBreakpoint('functionname()');
     var req = {