Implement ES6 unicode escapes.

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index c5bf0d977708df914299099f36f197a0e5b55eca..36150f73abeebaf479feeca544a2a03bc3da889e 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -4411,7 +4411,7 @@ RegExpTree* RegExpParser::ParseDisjunction() {
       case 'u': {
         Advance(2);
         uc32 value;
-        if (ParseHexEscape(4, &value)) {
+        if (ParseHexEscape(4, &value, true)) {
           builder->AddCharacter(value);
         } else {
           builder->AddCharacter('u');
@@ -4664,11 +4664,15 @@ uc32 RegExpParser::ParseOctalLiteral() {
 }
 
 
-bool RegExpParser::ParseHexEscape(int length, uc32 *value) {
+bool RegExpParser::ParseHexEscape(int length, uc32* value, bool allow_brace) {
   int start = position();
   uc32 val = 0;
-  bool done = false;
-  for (int i = 0; !done; i++) {
+  bool has_brace = false;
+  if (allow_brace && current() == '{') {
+    has_brace = true;
+    Advance();
+  }
+  for (int i = 0; i < length; ++i) {
     uc32 c = current();
     int d = HexValue(c);
     if (d < 0) {
@@ -4677,9 +4681,13 @@ bool RegExpParser::ParseHexEscape(int length, uc32 *value) {
     }
     val = val * 16 + d;
     Advance();
-    if (i == length - 1) {
-      done = true;
+  }
+  if (has_brace) {
+    if (current() != '}') {
+      Reset(start);
+      return false;
     }
+    Advance();
   }
   *value = val;
   return true;
@@ -4747,7 +4755,7 @@ uc32 RegExpParser::ParseClassCharacterEscape() {
     case 'u': {
       Advance();
       uc32 value;
-      if (ParseHexEscape(4, &value)) {
+      if (ParseHexEscape(4, &value, true)) {
         return value;
       }
       // If \u is not followed by a four-digit hexadecimal, treat it