Simplify scanner and generate better error message for legacy octals in templates

test/mjsunit/harmony/templates.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --harmony-templates --harmony-unicode
 
 var num = 5;
 var str = "str";
 function fn() { return "result"; }
 var obj = {
@@ skipping 458 matching lines @@
 
   {
     // block
   }`jkl`;
 })();
 
 
 (function testLegacyOctal() {
   assertEquals('\u0000', `\0`);
   assertEquals('\u0000a', `\0a`);
-  for (var i = 0; i < 10; i++) {
+  for (var i = 0; i < 8; i++) {
     var code = "`\\0" + i + "`";
     assertThrows(code, SyntaxError);
+    code = "(function(){})" + code;
+    assertThrows(code, SyntaxError);
   }
 
   assertEquals('\\0', String.raw`\0`);
 })();
 
 
 (function testSyntaxErrorsNonEscapeCharacter() {
   assertThrows("`\\x`", SyntaxError);
   assertThrows("`\\u`", SyntaxError);
-  for (var i = 1; i < 10; i++) {
+  for (var i = 1; i < 8; i++) {
     var code = "`\\" + i + "`";
     assertThrows(code, SyntaxError);
+    code = "(function(){})" + code;
+    assertThrows(code, SyntaxError);
   }
 })();
+
+
+(function testValidNumericEscapes() {
+  assertEquals("8", `\8`);
+  assertEquals("9", `\9`);
+  assertEquals("\u00008", `\08`);
+  assertEquals("\u00009", `\09`);
+})();