[proxy] fixing harmony/proxy.js tests and improving error messages + some drive-by fixes

test/mjsunit/harmony/regress/regress-2225.js

Index: test/mjsunit/harmony/regress/regress-2225.js
diff --git a/test/mjsunit/harmony/regress/regress-2225.js b/test/mjsunit/harmony/regress/regress-2225.js
index 12d3eee116a0c4ddd0269cb08832374b58df912e..4a4ccb23db58ebd9b69e0b6e40d64382c22ed98b 100644
--- a/test/mjsunit/harmony/regress/regress-2225.js
+++ b/test/mjsunit/harmony/regress/regress-2225.js
@@ -28,7 +28,7 @@
 // Flags: --harmony-proxies
 
 var proxy_has_x = false;
-var proxy = new Proxy({}, { getPropertyDescriptor:function(key) {
+var proxy = new Proxy({}, { getOwnPropertyDescriptor:function(t, key) {
   assertSame('x', key);
   if (proxy_has_x) {
     return { configurable:true, writable:false, value:19 };