Fix typo in fast path for scanning json strings.

src/json-parser.h

Index: src/json-parser.h
diff --git a/src/json-parser.h b/src/json-parser.h
index 0b8cb769ca679676b85b3dd8884500a480f23800..d940c140464bd2c1fe567eeafc75231f39ef2514 100644
--- a/src/json-parser.h
+++ b/src/json-parser.h
@@ -584,7 +584,7 @@ Handle<String> JsonParser<seq_ascii>::ScanJsonString() {
                                                         position_,
                                                         position);
       }
-      if (c0_ < 0x20) return Handle<String>::null();
+      if (c0 < 0x20) return Handle<String>::null();
       running_hash = StringHasher::AddCharacterCore(running_hash, c0);
       position++;
       if (position >= source_length_) return Handle<String>::null();