Add strict warning about trailing comma in object initializers being non-ECMA (50001, r=shaver).

js/src/js.msg

@@ -231,5 +231,6 @@ MSG_DEF(JSMSG_REDECLARED_VAR,         155, 2, JSEXN_TYPEERR, "redeclaration of {
 MSG_DEF(JSMSG_UNDECLARED_VAR,         156, 1, JSEXN_TYPEERR, "assignment to undeclared variable {0}")
 MSG_DEF(JSMSG_ANON_NO_RETURN_VALUE,   157, 0, JSEXN_TYPEERR, "anonymous function does not always return a value")
 MSG_DEF(JSMSG_DEPRECATED_USAGE,       158, 1, JSEXN_REFERENCEERR, "deprecated {0} usage")
-MSG_DEF(JSMSG_BAD_URI,				  159, 0, JSEXN_URIERR, "malformed URI sequence")
-MSG_DEF(JSMSG_GETTER_ONLY,			  160, 0, JSEXN_TYPEERR, "setting a property that has only a getter")
+MSG_DEF(JSMSG_BAD_URI,                159, 0, JSEXN_URIERR, "malformed URI sequence")
+MSG_DEF(JSMSG_GETTER_ONLY,            160, 0, JSEXN_TYPEERR, "setting a property that has only a getter")
+MSG_DEF(JSMSG_TRAILING_COMMA,         161, 0, JSEXN_SYNTAXERR, "trailing comma is not legal in ECMA-262 object initializers")

js/src/jsparse.c

@@ -2278,6 +2278,7 @@ MemberExpr(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc,
         pn2 = MemberExpr(cx, ts, tc, JS_FALSE);
         if (!pn2)
             return NULL;
+        pn->pn_op = JSOP_NEW;
         PN_INIT_LIST_1(pn, pn2);
 
         if (js_MatchToken(cx, ts, TOK_LP)) {
@@ -2497,7 +2498,8 @@ PrimaryExpr(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc)
                                 return NULL;
                             pn3->pn_atom = CURRENT_TOKEN(ts).t_atom;
                             pn3->pn_expr = NULL;
-                            /* have to fake a 'function' token */
+
+                            /* We have to fake a 'function' token here. */
                             CURRENT_TOKEN(ts).t_op = JSOP_NOP;
                             CURRENT_TOKEN(ts).type = TOK_FUNCTION;
                             pn2 = FunctionDef(cx, ts, tc, JS_TRUE);
@@ -2513,6 +2515,13 @@ PrimaryExpr(JSContext *cx, JSTokenStream *ts, JSTreeContext *tc)
                         pn3->pn_atom = CURRENT_TOKEN(ts).t_atom;
                     break;
                   case TOK_RC:
+                    if (JS_HAS_STRICT_OPTION(cx) &&
+                        !js_ReportCompileErrorNumber(cx, ts,
+                                                     JSREPORT_WARNING |
+                                                     JSREPORT_STRICT,
+                                                     JSMSG_TRAILING_COMMA)) {
+                        return NULL;
+                    }
                     goto end_obj_init;
                   default:
                     js_ReportCompileErrorNumber(cx, ts, JSREPORT_ERROR,