Issue #1302 followup - Add spec-compliance checks/errors

- Check for undefined/null regex flags (because...)
- Make it throw a typeerror instead of syntax error on non-global
- Generalize JS error messages for these checks.

js/src/builtin/RegExp.js

@@ -1042,6 +1042,9 @@ function RegExpMatchAll(string) {
     // Step 2.
     if (!IsObject(rx))
         ThrowTypeError(JSMSG_NOT_NONNULL_OBJECT, rx === null ? "null" : typeof rx);
+        
+    if (rx.flags === undefined || rx.flags === null)
+        ThrowTypeError(JSMSG_FLAGS_UNDEFINED_OR_NULL);
 
     // Step 3.
     var str = ToString(string);
@@ -1052,9 +1055,9 @@ function RegExpMatchAll(string) {
     // Step 5.
     var flags = ToString(rx.flags);
     
-    // Step 2.b.iii; located here because it needs |flags|.
+    // Step 2.b.iii; located here because it needs to check |flags|.
     if (!callFunction(std_String_includes, flags, "g")) {
-        ThrowTypeError(JSMSG_BAD_REGEXP_FLAG, "- matchAll requires g");
+        ThrowTypeError(JSMSG_REQUIRES_GLOBAL_REGEXP, "matchAll");
     }
     
     // Step 6.

js/src/js.msg

@@ -132,6 +132,8 @@ MSG_DEF(JSMSG_INVALID_NORMALIZE_FORM,  0, JSEXN_RANGEERR, "form must be one of '
 MSG_DEF(JSMSG_NEGATIVE_REPETITION_COUNT, 0, JSEXN_RANGEERR, "repeat count must be non-negative")
 MSG_DEF(JSMSG_NOT_A_CODEPOINT,         1, JSEXN_RANGEERR, "{0} is not a valid code point")
 MSG_DEF(JSMSG_RESULTING_STRING_TOO_LARGE, 0, JSEXN_RANGEERR, "repeat count must be less than infinity and not overflow maximum string size")
+MSG_DEF(JSMSG_FLAGS_UNDEFINED_OR_NULL, 0, JSEXN_TYPEERR, "'flags' property must neither be undefined nor null")
+MSG_DEF(JSMSG_REQUIRES_GLOBAL_REGEXP,  1, JSEXN_TYPEERR, "{0} must be called with a global RegExp")
 
 // Number
 MSG_DEF(JSMSG_BAD_RADIX,               0, JSEXN_RANGEERR, "radix must be an integer at least 2 and no greater than 36")