diff --git a/spdy/core/spdy_header_block.cc b/spdy/core/spdy_header_block.cc
new file mode 100644
index 0000000..dcf84b9
--- /dev/null
+++ b/spdy/core/spdy_header_block.cc
@@ -0,0 +1,401 @@
+// 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 "net/third_party/quiche/src/spdy/core/spdy_header_block.h"
+
+#include <string.h>
+
+#include <algorithm>
+#include <utility>
+
+#include "base/logging.h"
+#include "base/macros.h"
+#include "net/third_party/quiche/src/spdy/platform/api/spdy_estimate_memory_usage.h"
+#include "net/third_party/quiche/src/spdy/platform/api/spdy_ptr_util.h"
+#include "net/third_party/quiche/src/spdy/platform/api/spdy_string_utils.h"
+#include "net/third_party/quiche/src/spdy/platform/api/spdy_unsafe_arena.h"
+
+namespace spdy {
+namespace {
+
+// By default, linked_hash_map's internal map allocates space for 100 map
+// buckets on construction, which is larger than necessary.  Standard library
+// unordered map implementations use a list of prime numbers to set the bucket
+// count for a particular capacity.  |kInitialMapBuckets| is chosen to reduce
+// memory usage for small header blocks, at the cost of having to rehash for
+// large header blocks.
+const size_t kInitialMapBuckets = 11;
+
+// SpdyHeaderBlock::Storage allocates blocks of this size by default.
+const size_t kDefaultStorageBlockSize = 2048;
+
+const char kCookieKey[] = "cookie";
+const char kNullSeparator = 0;
+
+SpdyStringPiece SeparatorForKey(SpdyStringPiece key) {
+  if (key == kCookieKey) {
+    static SpdyStringPiece cookie_separator = "; ";
+    return cookie_separator;
+  } else {
+    return SpdyStringPiece(&kNullSeparator, 1);
+  }
+}
+
+}  // namespace
+
+// This class provides a backing store for SpdyStringPieces. It previously used
+// custom allocation logic, but now uses an UnsafeArena instead. It has the
+// property that SpdyStringPieces that refer to data in Storage are never
+// invalidated until the Storage is deleted or Clear() is called.
+//
+// Write operations always append to the last block. If there is not enough
+// space to perform the write, a new block is allocated, and any unused space
+// is wasted.
+class SpdyHeaderBlock::Storage {
+ public:
+  Storage() : arena_(kDefaultStorageBlockSize) {}
+  Storage(const Storage&) = delete;
+  Storage& operator=(const Storage&) = delete;
+
+  SpdyStringPiece Write(const SpdyStringPiece s) {
+    return SpdyStringPiece(arena_.Memdup(s.data(), s.size()), s.size());
+  }
+
+  // If |s| points to the most recent allocation from arena_, the arena will
+  // reclaim the memory. Otherwise, this method is a no-op.
+  void Rewind(const SpdyStringPiece s) {
+    arena_.Free(const_cast<char*>(s.data()), s.size());
+  }
+
+  void Clear() { arena_.Reset(); }
+
+  // Given a list of fragments and a separator, writes the fragments joined by
+  // the separator to a contiguous region of memory. Returns a SpdyStringPiece
+  // pointing to the region of memory.
+  SpdyStringPiece WriteFragments(const std::vector<SpdyStringPiece>& fragments,
+                                 SpdyStringPiece separator) {
+    if (fragments.empty()) {
+      return SpdyStringPiece();
+    }
+    size_t total_size = separator.size() * (fragments.size() - 1);
+    for (const auto fragment : fragments) {
+      total_size += fragment.size();
+    }
+    char* dst = arena_.Alloc(total_size);
+    size_t written = Join(dst, fragments, separator);
+    DCHECK_EQ(written, total_size);
+    return SpdyStringPiece(dst, total_size);
+  }
+
+  size_t bytes_allocated() const { return arena_.status().bytes_allocated(); }
+
+  // TODO(xunjieli): https://crbug.com/669108. Merge this with bytes_allocated()
+  size_t EstimateMemoryUsage() const {
+    return arena_.status().bytes_allocated();
+  }
+
+ private:
+  SpdyUnsafeArena arena_;
+};
+
+SpdyHeaderBlock::HeaderValue::HeaderValue(Storage* storage,
+                                          SpdyStringPiece key,
+                                          SpdyStringPiece initial_value)
+    : storage_(storage),
+      fragments_({initial_value}),
+      pair_({key, {}}),
+      size_(initial_value.size()),
+      separator_size_(SeparatorForKey(key).size()) {}
+
+SpdyHeaderBlock::HeaderValue::HeaderValue(HeaderValue&& other)
+    : storage_(other.storage_),
+      fragments_(std::move(other.fragments_)),
+      pair_(std::move(other.pair_)),
+      size_(other.size_),
+      separator_size_(other.separator_size_) {}
+
+SpdyHeaderBlock::HeaderValue& SpdyHeaderBlock::HeaderValue::operator=(
+    HeaderValue&& other) {
+  storage_ = other.storage_;
+  fragments_ = std::move(other.fragments_);
+  pair_ = std::move(other.pair_);
+  size_ = other.size_;
+  separator_size_ = other.separator_size_;
+  return *this;
+}
+
+SpdyHeaderBlock::HeaderValue::~HeaderValue() = default;
+
+SpdyStringPiece SpdyHeaderBlock::HeaderValue::ConsolidatedValue() const {
+  if (fragments_.empty()) {
+    return SpdyStringPiece();
+  }
+  if (fragments_.size() > 1) {
+    fragments_ = {
+        storage_->WriteFragments(fragments_, SeparatorForKey(pair_.first))};
+  }
+  return fragments_[0];
+}
+
+void SpdyHeaderBlock::HeaderValue::Append(SpdyStringPiece fragment) {
+  size_ += (fragment.size() + separator_size_);
+  fragments_.push_back(fragment);
+}
+
+const std::pair<SpdyStringPiece, SpdyStringPiece>&
+SpdyHeaderBlock::HeaderValue::as_pair() const {
+  pair_.second = ConsolidatedValue();
+  return pair_;
+}
+
+SpdyHeaderBlock::iterator::iterator(MapType::const_iterator it) : it_(it) {}
+
+SpdyHeaderBlock::iterator::iterator(const iterator& other) = default;
+
+SpdyHeaderBlock::iterator::~iterator() = default;
+
+SpdyHeaderBlock::ValueProxy::ValueProxy(
+    SpdyHeaderBlock::MapType* block,
+    SpdyHeaderBlock::Storage* storage,
+    SpdyHeaderBlock::MapType::iterator lookup_result,
+    const SpdyStringPiece key,
+    size_t* spdy_header_block_value_size)
+    : block_(block),
+      storage_(storage),
+      lookup_result_(lookup_result),
+      key_(key),
+      spdy_header_block_value_size_(spdy_header_block_value_size),
+      valid_(true) {}
+
+SpdyHeaderBlock::ValueProxy::ValueProxy(ValueProxy&& other)
+    : block_(other.block_),
+      storage_(other.storage_),
+      lookup_result_(other.lookup_result_),
+      key_(other.key_),
+      spdy_header_block_value_size_(other.spdy_header_block_value_size_),
+      valid_(true) {
+  other.valid_ = false;
+}
+
+SpdyHeaderBlock::ValueProxy& SpdyHeaderBlock::ValueProxy::operator=(
+    SpdyHeaderBlock::ValueProxy&& other) {
+  block_ = other.block_;
+  storage_ = other.storage_;
+  lookup_result_ = other.lookup_result_;
+  key_ = other.key_;
+  valid_ = true;
+  other.valid_ = false;
+  spdy_header_block_value_size_ = other.spdy_header_block_value_size_;
+  return *this;
+}
+
+SpdyHeaderBlock::ValueProxy::~ValueProxy() {
+  // If the ValueProxy is destroyed while lookup_result_ == block_->end(),
+  // the assignment operator was never used, and the block's Storage can
+  // reclaim the memory used by the key. This makes lookup-only access to
+  // SpdyHeaderBlock through operator[] memory-neutral.
+  if (valid_ && lookup_result_ == block_->end()) {
+    storage_->Rewind(key_);
+  }
+}
+
+SpdyHeaderBlock::ValueProxy& SpdyHeaderBlock::ValueProxy::operator=(
+    const SpdyStringPiece value) {
+  *spdy_header_block_value_size_ += value.size();
+  if (lookup_result_ == block_->end()) {
+    DVLOG(1) << "Inserting: (" << key_ << ", " << value << ")";
+    lookup_result_ =
+        block_
+            ->emplace(std::make_pair(
+                key_, HeaderValue(storage_, key_, storage_->Write(value))))
+            .first;
+  } else {
+    DVLOG(1) << "Updating key: " << key_ << " with value: " << value;
+    *spdy_header_block_value_size_ -= lookup_result_->second.SizeEstimate();
+    lookup_result_->second =
+        HeaderValue(storage_, key_, storage_->Write(value));
+  }
+  return *this;
+}
+
+SpdyString SpdyHeaderBlock::ValueProxy::as_string() const {
+  if (lookup_result_ == block_->end()) {
+    return "";
+  } else {
+    return SpdyString(lookup_result_->second.value());
+  }
+}
+
+SpdyHeaderBlock::SpdyHeaderBlock() : block_(kInitialMapBuckets) {}
+
+SpdyHeaderBlock::SpdyHeaderBlock(SpdyHeaderBlock&& other)
+    : block_(kInitialMapBuckets) {
+  block_.swap(other.block_);
+  storage_.swap(other.storage_);
+  key_size_ = other.key_size_;
+  value_size_ = other.value_size_;
+}
+
+SpdyHeaderBlock::~SpdyHeaderBlock() = default;
+
+SpdyHeaderBlock& SpdyHeaderBlock::operator=(SpdyHeaderBlock&& other) {
+  block_.swap(other.block_);
+  storage_.swap(other.storage_);
+  key_size_ = other.key_size_;
+  value_size_ = other.value_size_;
+  return *this;
+}
+
+SpdyHeaderBlock SpdyHeaderBlock::Clone() const {
+  SpdyHeaderBlock copy;
+  for (const auto& p : *this) {
+    copy.AppendHeader(p.first, p.second);
+  }
+  return copy;
+}
+
+bool SpdyHeaderBlock::operator==(const SpdyHeaderBlock& other) const {
+  return size() == other.size() && std::equal(begin(), end(), other.begin());
+}
+
+bool SpdyHeaderBlock::operator!=(const SpdyHeaderBlock& other) const {
+  return !(operator==(other));
+}
+
+SpdyString SpdyHeaderBlock::DebugString() const {
+  if (empty()) {
+    return "{}";
+  }
+
+  SpdyString output = "\n{\n";
+  for (auto it = begin(); it != end(); ++it) {
+    SpdyStrAppend(&output, "  ", it->first, " ", it->second, "\n");
+  }
+  SpdyStrAppend(&output, "}\n");
+  return output;
+}
+
+void SpdyHeaderBlock::erase(SpdyStringPiece key) {
+  auto iter = block_.find(key);
+  if (iter != block_.end()) {
+    DVLOG(1) << "Erasing header with name: " << key;
+    key_size_ -= key.size();
+    value_size_ -= iter->second.SizeEstimate();
+    block_.erase(iter);
+  }
+}
+
+void SpdyHeaderBlock::clear() {
+  key_size_ = 0;
+  value_size_ = 0;
+  block_.clear();
+  storage_.reset();
+}
+
+void SpdyHeaderBlock::insert(const SpdyHeaderBlock::value_type& value) {
+  // TODO(birenroy): Write new value in place of old value, if it fits.
+  value_size_ += value.second.size();
+
+  auto iter = block_.find(value.first);
+  if (iter == block_.end()) {
+    DVLOG(1) << "Inserting: (" << value.first << ", " << value.second << ")";
+    AppendHeader(value.first, value.second);
+  } else {
+    DVLOG(1) << "Updating key: " << iter->first
+             << " with value: " << value.second;
+    value_size_ -= iter->second.SizeEstimate();
+    auto* storage = GetStorage();
+    iter->second =
+        HeaderValue(storage, iter->first, storage->Write(value.second));
+  }
+}
+
+SpdyHeaderBlock::ValueProxy SpdyHeaderBlock::operator[](
+    const SpdyStringPiece key) {
+  DVLOG(2) << "Operator[] saw key: " << key;
+  SpdyStringPiece out_key;
+  auto iter = block_.find(key);
+  if (iter == block_.end()) {
+    // We write the key first, to assure that the ValueProxy has a
+    // reference to a valid SpdyStringPiece in its operator=.
+    out_key = WriteKey(key);
+    DVLOG(2) << "Key written as: " << std::hex
+             << static_cast<const void*>(key.data()) << ", " << std::dec
+             << key.size();
+  } else {
+    out_key = iter->first;
+  }
+  return ValueProxy(&block_, GetStorage(), iter, out_key, &value_size_);
+}
+
+void SpdyHeaderBlock::AppendValueOrAddHeader(const SpdyStringPiece key,
+                                             const SpdyStringPiece value) {
+  value_size_ += value.size();
+
+  auto iter = block_.find(key);
+  if (iter == block_.end()) {
+    DVLOG(1) << "Inserting: (" << key << ", " << value << ")";
+
+    AppendHeader(key, value);
+    return;
+  }
+  DVLOG(1) << "Updating key: " << iter->first << "; appending value: " << value;
+  value_size_ += SeparatorForKey(key).size();
+  iter->second.Append(GetStorage()->Write(value));
+}
+
+size_t SpdyHeaderBlock::EstimateMemoryUsage() const {
+  // TODO(xunjieli): https://crbug.com/669108. Also include |block_| when EMU()
+  // supports linked_hash_map.
+  return SpdyEstimateMemoryUsage(storage_);
+}
+
+void SpdyHeaderBlock::AppendHeader(const SpdyStringPiece key,
+                                   const SpdyStringPiece value) {
+  auto backed_key = WriteKey(key);
+  auto* storage = GetStorage();
+  block_.emplace(std::make_pair(
+      backed_key, HeaderValue(storage, backed_key, storage->Write(value))));
+}
+
+SpdyHeaderBlock::Storage* SpdyHeaderBlock::GetStorage() {
+  if (storage_ == nullptr) {
+    storage_ = SpdyMakeUnique<Storage>();
+  }
+  return storage_.get();
+}
+
+SpdyStringPiece SpdyHeaderBlock::WriteKey(const SpdyStringPiece key) {
+  key_size_ += key.size();
+  return GetStorage()->Write(key);
+}
+
+size_t SpdyHeaderBlock::bytes_allocated() const {
+  if (storage_ == nullptr) {
+    return 0;
+  } else {
+    return storage_->bytes_allocated();
+  }
+}
+
+size_t Join(char* dst,
+            const std::vector<SpdyStringPiece>& fragments,
+            SpdyStringPiece separator) {
+  if (fragments.empty()) {
+    return 0;
+  }
+  auto* original_dst = dst;
+  auto it = fragments.begin();
+  memcpy(dst, it->data(), it->size());
+  dst += it->size();
+  for (++it; it != fragments.end(); ++it) {
+    memcpy(dst, separator.data(), separator.size());
+    dst += separator.size();
+    memcpy(dst, it->data(), it->size());
+    dst += it->size();
+  }
+  return dst - original_dst;
+}
+
+}  // namespace spdy