diff --git a/base/json/json_parser.cc b/base/json/json_parser.cc
new file mode 100644
index 0000000..dfe246c
--- /dev/null
+++ b/base/json/json_parser.cc
@@ -0,0 +1,755 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/json/json_parser.h"
+
+#include <cmath>
+#include <utility>
+#include <vector>
+
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/numerics/safe_conversions.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "base/strings/stringprintf.h"
+#include "base/strings/utf_string_conversion_utils.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/third_party/icu/icu_utf.h"
+#include "base/values.h"
+
+namespace base {
+namespace internal {
+
+namespace {
+
+const int32_t kExtendedASCIIStart = 0x80;
+
+// Simple class that checks for maximum recursion/"stack overflow."
+class StackMarker {
+ public:
+  StackMarker(int max_depth, int* depth)
+      : max_depth_(max_depth), depth_(depth) {
+    ++(*depth_);
+    DCHECK_LE(*depth_, max_depth_);
+  }
+  ~StackMarker() {
+    --(*depth_);
+  }
+
+  bool IsTooDeep() const { return *depth_ >= max_depth_; }
+
+ private:
+  const int max_depth_;
+  int* const depth_;
+
+  DISALLOW_COPY_AND_ASSIGN(StackMarker);
+};
+
+constexpr uint32_t kUnicodeReplacementPoint = 0xFFFD;
+
+}  // namespace
+
+// This is U+FFFD.
+const char kUnicodeReplacementString[] = "\xEF\xBF\xBD";
+
+JSONParser::JSONParser(int options, int max_depth)
+    : options_(options),
+      max_depth_(max_depth),
+      index_(0),
+      stack_depth_(0),
+      line_number_(0),
+      index_last_line_(0),
+      error_code_(JSONReader::JSON_NO_ERROR),
+      error_line_(0),
+      error_column_(0) {
+  CHECK_LE(max_depth, JSONReader::kStackMaxDepth);
+}
+
+JSONParser::~JSONParser() = default;
+
+Optional<Value> JSONParser::Parse(StringPiece input) {
+  input_ = input;
+  index_ = 0;
+  line_number_ = 1;
+  index_last_line_ = 0;
+
+  error_code_ = JSONReader::JSON_NO_ERROR;
+  error_line_ = 0;
+  error_column_ = 0;
+
+  // ICU and ReadUnicodeCharacter() use int32_t for lengths, so ensure
+  // that the index_ will not overflow when parsing.
+  if (!base::IsValueInRangeForNumericType<int32_t>(input.length())) {
+    ReportError(JSONReader::JSON_TOO_LARGE, 0);
+    return nullopt;
+  }
+
+  // When the input JSON string starts with a UTF-8 Byte-Order-Mark,
+  // advance the start position to avoid the ParseNextToken function mis-
+  // treating a Unicode BOM as an invalid character and returning NULL.
+  ConsumeIfMatch("\xEF\xBB\xBF");
+
+  // Parse the first and any nested tokens.
+  Optional<Value> root(ParseNextToken());
+  if (!root)
+    return nullopt;
+
+  // Make sure the input stream is at an end.
+  if (GetNextToken() != T_END_OF_INPUT) {
+    ReportError(JSONReader::JSON_UNEXPECTED_DATA_AFTER_ROOT, 1);
+    return nullopt;
+  }
+
+  return root;
+}
+
+JSONReader::JsonParseError JSONParser::error_code() const {
+  return error_code_;
+}
+
+std::string JSONParser::GetErrorMessage() const {
+  return FormatErrorMessage(error_line_, error_column_,
+      JSONReader::ErrorCodeToString(error_code_));
+}
+
+int JSONParser::error_line() const {
+  return error_line_;
+}
+
+int JSONParser::error_column() const {
+  return error_column_;
+}
+
+// StringBuilder ///////////////////////////////////////////////////////////////
+
+JSONParser::StringBuilder::StringBuilder() : StringBuilder(nullptr) {}
+
+JSONParser::StringBuilder::StringBuilder(const char* pos)
+    : pos_(pos), length_(0) {}
+
+JSONParser::StringBuilder::~StringBuilder() = default;
+
+JSONParser::StringBuilder& JSONParser::StringBuilder::operator=(
+    StringBuilder&& other) = default;
+
+void JSONParser::StringBuilder::Append(uint32_t point) {
+  DCHECK(IsValidCharacter(point));
+
+  if (point < kExtendedASCIIStart && !string_) {
+    DCHECK_EQ(static_cast<char>(point), pos_[length_]);
+    ++length_;
+  } else {
+    Convert();
+    if (UNLIKELY(point == kUnicodeReplacementPoint)) {
+      string_->append(kUnicodeReplacementString);
+    } else {
+      WriteUnicodeCharacter(point, &*string_);
+    }
+  }
+}
+
+void JSONParser::StringBuilder::Convert() {
+  if (string_)
+    return;
+  string_.emplace(pos_, length_);
+}
+
+std::string JSONParser::StringBuilder::DestructiveAsString() {
+  if (string_)
+    return std::move(*string_);
+  return std::string(pos_, length_);
+}
+
+// JSONParser private //////////////////////////////////////////////////////////
+
+Optional<StringPiece> JSONParser::PeekChars(int count) {
+  if (static_cast<size_t>(index_) + count > input_.length())
+    return nullopt;
+  // Using StringPiece::substr() is significantly slower (according to
+  // base_perftests) than constructing a substring manually.
+  return StringPiece(input_.data() + index_, count);
+}
+
+Optional<char> JSONParser::PeekChar() {
+  Optional<StringPiece> chars = PeekChars(1);
+  if (chars)
+    return (*chars)[0];
+  return nullopt;
+}
+
+Optional<StringPiece> JSONParser::ConsumeChars(int count) {
+  Optional<StringPiece> chars = PeekChars(count);
+  if (chars)
+    index_ += count;
+  return chars;
+}
+
+Optional<char> JSONParser::ConsumeChar() {
+  Optional<StringPiece> chars = ConsumeChars(1);
+  if (chars)
+    return (*chars)[0];
+  return nullopt;
+}
+
+const char* JSONParser::pos() {
+  CHECK_LE(static_cast<size_t>(index_), input_.length());
+  return input_.data() + index_;
+}
+
+JSONParser::Token JSONParser::GetNextToken() {
+  EatWhitespaceAndComments();
+
+  Optional<char> c = PeekChar();
+  if (!c)
+    return T_END_OF_INPUT;
+
+  switch (*c) {
+    case '{':
+      return T_OBJECT_BEGIN;
+    case '}':
+      return T_OBJECT_END;
+    case '[':
+      return T_ARRAY_BEGIN;
+    case ']':
+      return T_ARRAY_END;
+    case '"':
+      return T_STRING;
+    case '0':
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+    case '5':
+    case '6':
+    case '7':
+    case '8':
+    case '9':
+    case '-':
+      return T_NUMBER;
+    case 't':
+      return T_BOOL_TRUE;
+    case 'f':
+      return T_BOOL_FALSE;
+    case 'n':
+      return T_NULL;
+    case ',':
+      return T_LIST_SEPARATOR;
+    case ':':
+      return T_OBJECT_PAIR_SEPARATOR;
+    default:
+      return T_INVALID_TOKEN;
+  }
+}
+
+void JSONParser::EatWhitespaceAndComments() {
+  while (Optional<char> c = PeekChar()) {
+    switch (*c) {
+      case '\r':
+      case '\n':
+        index_last_line_ = index_;
+        // Don't increment line_number_ twice for "\r\n".
+        if (!(c == '\n' && index_ > 0 && input_[index_ - 1] == '\r')) {
+          ++line_number_;
+        }
+        FALLTHROUGH;
+      case ' ':
+      case '\t':
+        ConsumeChar();
+        break;
+      case '/':
+        if (!EatComment())
+          return;
+        break;
+      default:
+        return;
+    }
+  }
+}
+
+bool JSONParser::EatComment() {
+  Optional<StringPiece> comment_start = ConsumeChars(2);
+  if (!comment_start)
+    return false;
+
+  if (comment_start == "//") {
+    // Single line comment, read to newline.
+    while (Optional<char> c = PeekChar()) {
+      if (c == '\n' || c == '\r')
+        return true;
+      ConsumeChar();
+    }
+  } else if (comment_start == "/*") {
+    char previous_char = '\0';
+    // Block comment, read until end marker.
+    while (Optional<char> c = PeekChar()) {
+      if (previous_char == '*' && c == '/') {
+        // EatWhitespaceAndComments will inspect pos(), which will still be on
+        // the last / of the comment, so advance once more (which may also be
+        // end of input).
+        ConsumeChar();
+        return true;
+      }
+      previous_char = *ConsumeChar();
+    }
+
+    // If the comment is unterminated, GetNextToken will report T_END_OF_INPUT.
+  }
+
+  return false;
+}
+
+Optional<Value> JSONParser::ParseNextToken() {
+  return ParseToken(GetNextToken());
+}
+
+Optional<Value> JSONParser::ParseToken(Token token) {
+  switch (token) {
+    case T_OBJECT_BEGIN:
+      return ConsumeDictionary();
+    case T_ARRAY_BEGIN:
+      return ConsumeList();
+    case T_STRING:
+      return ConsumeString();
+    case T_NUMBER:
+      return ConsumeNumber();
+    case T_BOOL_TRUE:
+    case T_BOOL_FALSE:
+    case T_NULL:
+      return ConsumeLiteral();
+    default:
+      ReportError(JSONReader::JSON_UNEXPECTED_TOKEN, 1);
+      return nullopt;
+  }
+}
+
+Optional<Value> JSONParser::ConsumeDictionary() {
+  if (ConsumeChar() != '{') {
+    ReportError(JSONReader::JSON_UNEXPECTED_TOKEN, 1);
+    return nullopt;
+  }
+
+  StackMarker depth_check(max_depth_, &stack_depth_);
+  if (depth_check.IsTooDeep()) {
+    ReportError(JSONReader::JSON_TOO_MUCH_NESTING, 0);
+    return nullopt;
+  }
+
+  std::vector<Value::DictStorage::value_type> dict_storage;
+
+  Token token = GetNextToken();
+  while (token != T_OBJECT_END) {
+    if (token != T_STRING) {
+      ReportError(JSONReader::JSON_UNQUOTED_DICTIONARY_KEY, 1);
+      return nullopt;
+    }
+
+    // First consume the key.
+    StringBuilder key;
+    if (!ConsumeStringRaw(&key)) {
+      return nullopt;
+    }
+
+    // Read the separator.
+    token = GetNextToken();
+    if (token != T_OBJECT_PAIR_SEPARATOR) {
+      ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
+      return nullopt;
+    }
+
+    // The next token is the value. Ownership transfers to |dict|.
+    ConsumeChar();
+    Optional<Value> value = ParseNextToken();
+    if (!value) {
+      // ReportError from deeper level.
+      return nullopt;
+    }
+
+    dict_storage.emplace_back(key.DestructiveAsString(),
+                              std::make_unique<Value>(std::move(*value)));
+
+    token = GetNextToken();
+    if (token == T_LIST_SEPARATOR) {
+      ConsumeChar();
+      token = GetNextToken();
+      if (token == T_OBJECT_END && !(options_ & JSON_ALLOW_TRAILING_COMMAS)) {
+        ReportError(JSONReader::JSON_TRAILING_COMMA, 1);
+        return nullopt;
+      }
+    } else if (token != T_OBJECT_END) {
+      ReportError(JSONReader::JSON_SYNTAX_ERROR, 0);
+      return nullopt;
+    }
+  }
+
+  ConsumeChar();  // Closing '}'.
+
+  return Value(Value::DictStorage(std::move(dict_storage), KEEP_LAST_OF_DUPES));
+}
+
+Optional<Value> JSONParser::ConsumeList() {
+  if (ConsumeChar() != '[') {
+    ReportError(JSONReader::JSON_UNEXPECTED_TOKEN, 1);
+    return nullopt;
+  }
+
+  StackMarker depth_check(max_depth_, &stack_depth_);
+  if (depth_check.IsTooDeep()) {
+    ReportError(JSONReader::JSON_TOO_MUCH_NESTING, 0);
+    return nullopt;
+  }
+
+  Value::ListStorage list_storage;
+
+  Token token = GetNextToken();
+  while (token != T_ARRAY_END) {
+    Optional<Value> item = ParseToken(token);
+    if (!item) {
+      // ReportError from deeper level.
+      return nullopt;
+    }
+
+    list_storage.push_back(std::move(*item));
+
+    token = GetNextToken();
+    if (token == T_LIST_SEPARATOR) {
+      ConsumeChar();
+      token = GetNextToken();
+      if (token == T_ARRAY_END && !(options_ & JSON_ALLOW_TRAILING_COMMAS)) {
+        ReportError(JSONReader::JSON_TRAILING_COMMA, 1);
+        return nullopt;
+      }
+    } else if (token != T_ARRAY_END) {
+      ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
+      return nullopt;
+    }
+  }
+
+  ConsumeChar();  // Closing ']'.
+
+  return Value(std::move(list_storage));
+}
+
+Optional<Value> JSONParser::ConsumeString() {
+  StringBuilder string;
+  if (!ConsumeStringRaw(&string))
+    return nullopt;
+
+  return Value(string.DestructiveAsString());
+}
+
+bool JSONParser::ConsumeStringRaw(StringBuilder* out) {
+  if (ConsumeChar() != '"') {
+    ReportError(JSONReader::JSON_UNEXPECTED_TOKEN, 1);
+    return false;
+  }
+
+  // StringBuilder will internally build a StringPiece unless a UTF-16
+  // conversion occurs, at which point it will perform a copy into a
+  // std::string.
+  StringBuilder string(pos());
+
+  while (PeekChar()) {
+    uint32_t next_char = 0;
+    if (!ReadUnicodeCharacter(input_.data(),
+                              static_cast<int32_t>(input_.length()),
+                              &index_,
+                              &next_char) ||
+        !IsValidCharacter(next_char)) {
+      if ((options_ & JSON_REPLACE_INVALID_CHARACTERS) == 0) {
+        ReportError(JSONReader::JSON_UNSUPPORTED_ENCODING, 1);
+        return false;
+      }
+      ConsumeChar();
+      string.Append(kUnicodeReplacementPoint);
+      continue;
+    }
+
+    if (next_char == '"') {
+      ConsumeChar();
+      *out = std::move(string);
+      return true;
+    } else if (next_char != '\\') {
+      // If this character is not an escape sequence...
+      ConsumeChar();
+      string.Append(next_char);
+    } else {
+      // And if it is an escape sequence, the input string will be adjusted
+      // (either by combining the two characters of an encoded escape sequence,
+      // or with a UTF conversion), so using StringPiece isn't possible -- force
+      // a conversion.
+      string.Convert();
+
+      // Read past the escape '\' and ensure there's a character following.
+      Optional<StringPiece> escape_sequence = ConsumeChars(2);
+      if (!escape_sequence) {
+        ReportError(JSONReader::JSON_INVALID_ESCAPE, 0);
+        return false;
+      }
+
+      switch ((*escape_sequence)[1]) {
+        // Allowed esape sequences:
+        case 'x': {  // UTF-8 sequence.
+          // UTF-8 \x escape sequences are not allowed in the spec, but they
+          // are supported here for backwards-compatiblity with the old parser.
+          escape_sequence = ConsumeChars(2);
+          if (!escape_sequence) {
+            ReportError(JSONReader::JSON_INVALID_ESCAPE, -2);
+            return false;
+          }
+
+          int hex_digit = 0;
+          if (!HexStringToInt(*escape_sequence, &hex_digit) ||
+              !IsValidCharacter(hex_digit)) {
+            ReportError(JSONReader::JSON_INVALID_ESCAPE, -2);
+            return false;
+          }
+
+          string.Append(hex_digit);
+          break;
+        }
+        case 'u': {  // UTF-16 sequence.
+          // UTF units are of the form \uXXXX.
+          uint32_t code_point;
+          if (!DecodeUTF16(&code_point)) {
+            ReportError(JSONReader::JSON_INVALID_ESCAPE, 0);
+            return false;
+          }
+          string.Append(code_point);
+          break;
+        }
+        case '"':
+          string.Append('"');
+          break;
+        case '\\':
+          string.Append('\\');
+          break;
+        case '/':
+          string.Append('/');
+          break;
+        case 'b':
+          string.Append('\b');
+          break;
+        case 'f':
+          string.Append('\f');
+          break;
+        case 'n':
+          string.Append('\n');
+          break;
+        case 'r':
+          string.Append('\r');
+          break;
+        case 't':
+          string.Append('\t');
+          break;
+        case 'v':  // Not listed as valid escape sequence in the RFC.
+          string.Append('\v');
+          break;
+        // All other escape squences are illegal.
+        default:
+          ReportError(JSONReader::JSON_INVALID_ESCAPE, 0);
+          return false;
+      }
+    }
+  }
+
+  ReportError(JSONReader::JSON_SYNTAX_ERROR, 0);
+  return false;
+}
+
+// Entry is at the first X in \uXXXX.
+bool JSONParser::DecodeUTF16(uint32_t* out_code_point) {
+  Optional<StringPiece> escape_sequence = ConsumeChars(4);
+  if (!escape_sequence)
+    return false;
+
+  // Consume the UTF-16 code unit, which may be a high surrogate.
+  int code_unit16_high = 0;
+  if (!HexStringToInt(*escape_sequence, &code_unit16_high))
+    return false;
+
+  // If this is a high surrogate, consume the next code unit to get the
+  // low surrogate.
+  if (CBU16_IS_SURROGATE(code_unit16_high)) {
+    // Make sure this is the high surrogate. If not, it's an encoding
+    // error.
+    if (!CBU16_IS_SURROGATE_LEAD(code_unit16_high))
+      return false;
+
+    // Make sure that the token has more characters to consume the
+    // lower surrogate.
+    if (!ConsumeIfMatch("\\u"))
+      return false;
+
+    escape_sequence = ConsumeChars(4);
+    if (!escape_sequence)
+      return false;
+
+    int code_unit16_low = 0;
+    if (!HexStringToInt(*escape_sequence, &code_unit16_low))
+      return false;
+
+    if (!CBU16_IS_TRAIL(code_unit16_low))
+      return false;
+
+    uint32_t code_point =
+        CBU16_GET_SUPPLEMENTARY(code_unit16_high, code_unit16_low);
+    if (!IsValidCharacter(code_point))
+      return false;
+
+    *out_code_point = code_point;
+  } else {
+    // Not a surrogate.
+    DCHECK(CBU16_IS_SINGLE(code_unit16_high));
+    if (!IsValidCharacter(code_unit16_high)) {
+      if ((options_ & JSON_REPLACE_INVALID_CHARACTERS) == 0) {
+        return false;
+      }
+      *out_code_point = kUnicodeReplacementPoint;
+      return true;
+    }
+
+    *out_code_point = code_unit16_high;
+  }
+
+  return true;
+}
+
+Optional<Value> JSONParser::ConsumeNumber() {
+  const char* num_start = pos();
+  const int start_index = index_;
+  int end_index = start_index;
+
+  if (PeekChar() == '-')
+    ConsumeChar();
+
+  if (!ReadInt(false)) {
+    ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
+    return nullopt;
+  }
+  end_index = index_;
+
+  // The optional fraction part.
+  if (PeekChar() == '.') {
+    ConsumeChar();
+    if (!ReadInt(true)) {
+      ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
+      return nullopt;
+    }
+    end_index = index_;
+  }
+
+  // Optional exponent part.
+  Optional<char> c = PeekChar();
+  if (c == 'e' || c == 'E') {
+    ConsumeChar();
+    if (PeekChar() == '-' || PeekChar() == '+') {
+      ConsumeChar();
+    }
+    if (!ReadInt(true)) {
+      ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
+      return nullopt;
+    }
+    end_index = index_;
+  }
+
+  // ReadInt is greedy because numbers have no easily detectable sentinel,
+  // so save off where the parser should be on exit (see Consume invariant at
+  // the top of the header), then make sure the next token is one which is
+  // valid.
+  int exit_index = index_;
+
+  switch (GetNextToken()) {
+    case T_OBJECT_END:
+    case T_ARRAY_END:
+    case T_LIST_SEPARATOR:
+    case T_END_OF_INPUT:
+      break;
+    default:
+      ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
+      return nullopt;
+  }
+
+  index_ = exit_index;
+
+  StringPiece num_string(num_start, end_index - start_index);
+
+  int num_int;
+  if (StringToInt(num_string, &num_int))
+    return Value(num_int);
+
+  double num_double;
+  if (StringToDouble(num_string.as_string(), &num_double) &&
+      std::isfinite(num_double)) {
+    return Value(num_double);
+  }
+
+  return nullopt;
+}
+
+bool JSONParser::ReadInt(bool allow_leading_zeros) {
+  size_t len = 0;
+  char first = 0;
+
+  while (Optional<char> c = PeekChar()) {
+    if (!IsAsciiDigit(c))
+      break;
+
+    if (len == 0)
+      first = *c;
+
+    ++len;
+    ConsumeChar();
+  }
+
+  if (len == 0)
+    return false;
+
+  if (!allow_leading_zeros && len > 1 && first == '0')
+    return false;
+
+  return true;
+}
+
+Optional<Value> JSONParser::ConsumeLiteral() {
+  if (ConsumeIfMatch("true")) {
+    return Value(true);
+  } else if (ConsumeIfMatch("false")) {
+    return Value(false);
+  } else if (ConsumeIfMatch("null")) {
+    return Value(Value::Type::NONE);
+  } else {
+    ReportError(JSONReader::JSON_SYNTAX_ERROR, 1);
+    return nullopt;
+  }
+}
+
+bool JSONParser::ConsumeIfMatch(StringPiece match) {
+  if (match == PeekChars(match.size())) {
+    ConsumeChars(match.size());
+    return true;
+  }
+  return false;
+}
+
+void JSONParser::ReportError(JSONReader::JsonParseError code,
+                             int column_adjust) {
+  error_code_ = code;
+  error_line_ = line_number_;
+  error_column_ = index_ - index_last_line_ + column_adjust;
+}
+
+// static
+std::string JSONParser::FormatErrorMessage(int line, int column,
+                                           const std::string& description) {
+  if (line || column) {
+    return StringPrintf("Line: %i, column: %i, %s",
+        line, column, description.c_str());
+  }
+  return description;
+}
+
+}  // namespace internal
+}  // namespace base