Correctly expand literal buffer for surrogate pairs.

src/scanner.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.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #ifndef V8_SCANNER_H_
 #define V8_SCANNER_H_
 
 #include "src/allocation.h"
@@ skipping 201 matching lines @@
       }
       ConvertToTwoByte();
     }
     if (code_unit <= unibrow::Utf16::kMaxNonSurrogateCharCode) {
       *reinterpret_cast<uint16_t*>(&backing_store_[position_]) = code_unit;
       position_ += kUC16Size;
     } else {
       *reinterpret_cast<uint16_t*>(&backing_store_[position_]) =
           unibrow::Utf16::LeadSurrogate(code_unit);
       position_ += kUC16Size;
+      if (position_ >= backing_store_.length()) ExpandBuffer();
       *reinterpret_cast<uint16_t*>(&backing_store_[position_]) =
           unibrow::Utf16::TrailSurrogate(code_unit);
       position_ += kUC16Size;
     }
   }
 
   bool is_one_byte() const { return is_one_byte_; }
 
   bool is_contextual_keyword(Vector<const char> keyword) const {
     return is_one_byte() && keyword.length() == position_ &&
@@ skipping 446 matching lines @@
   bool harmony_modules_;
   // Whether we scan 0o777 and 0b111 as numbers.
   bool harmony_numeric_literals_;
   // Whether we scan 'class', 'extends', 'static' and 'super' as keywords.
   bool harmony_classes_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCANNER_H_