[json parser] remove dead code path.

src/parsing/json-parser.h

 // Copyright 2011 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.
 
 #ifndef V8_PARSING_JSON_PARSER_H_
 #define V8_PARSING_JSON_PARSER_H_
 
 #include "src/char-predicates.h"
 #include "src/conversions.h"
 #include "src/debug/debug.h"
@@ skipping 743 matching lines @@
     do {
       if (c0 == '\\') {
         c0_ = c0;
         int beg_pos = position_;
         position_ = position;
         return SlowScanJsonString<SeqOneByteString, uint8_t>(source_,
                                                              beg_pos,
                                                              position_);
       }
       if (c0 < 0x20) return Handle<String>::null();
-      if (static_cast<uint32_t>(c0) >
-          unibrow::Utf16::kMaxNonSurrogateCharCode) {
-        running_hash =
-            StringHasher::AddCharacterCore(running_hash,
-                                           unibrow::Utf16::LeadSurrogate(c0));
-        running_hash =
-            StringHasher::AddCharacterCore(running_hash,
-                                           unibrow::Utf16::TrailSurrogate(c0));
-      } else {
-        running_hash = StringHasher::AddCharacterCore(running_hash, c0);
-      }
+      running_hash = StringHasher::AddCharacterCore(running_hash,
+                                                    static_cast<uint16_t>(c0));
       position++;
       if (position >= source_length_) return Handle<String>::null();
       c0 = seq_source_->SeqOneByteStringGet(position);
     } while (c0 != '"');
     int length = position - position_;
     uint32_t hash = (length <= String::kMaxHashCalcLength)
                         ? StringHasher::GetHashCore(running_hash)
                         : static_cast<uint32_t>(length);
     Vector<const uint8_t> string_vector(
         seq_source_->GetChars() + position_, length);
@@ skipping 57 matching lines @@
   DCHECK_EQ('"', c0_);
   // Advance past the last '"'.
   AdvanceSkipWhitespace();
   return result;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_JSON_PARSER_H_