Bug 1094545. Expose the URLSearchParams API in system globals. r=bholley

dom/bindings/Codegen.py

@@ -11882,6 +11882,7 @@ class CGResolveSystemBinding(CGAbstractMethod):
     def definition_body(self):
         descriptors = self.config.getDescriptors(hasInterfaceObject=True,
                                                  isExposedInSystemGlobals=True,
+                                                 workers=False,
                                                  register=True,
                                                  skipGen=False)
 

dom/webidl/URLSearchParams.webidl

@@ -15,7 +15,7 @@
 
 [Constructor(optional USVString init = ""),
  Constructor(URLSearchParams init),
- Exposed=(Window,Worker)]
+ Exposed=(Window,Worker,System)]
 interface URLSearchParams {
   void append(USVString name, USVString value);
   void delete(USVString name);