Remove //net (except for Android test stuff) and sdch

net/disk_cache/blockfile/backend_impl_v3.cc

Index: net/disk_cache/blockfile/backend_impl_v3.cc
diff --git a/net/disk_cache/blockfile/backend_impl_v3.cc b/net/disk_cache/blockfile/backend_impl_v3.cc
deleted file mode 100644
index 961575510e5f85e9bbedb0e6557f2c897b0238c8..0000000000000000000000000000000000000000
--- a/net/disk_cache/blockfile/backend_impl_v3.cc
+++ /dev/null
@@ -1,1535 +0,0 @@
-// 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/disk_cache/blockfile/backend_impl_v3.h"
-
-#include "base/bind.h"
-#include "base/bind_helpers.h"
-#include "base/files/file_path.h"
-#include "base/files/file_util.h"
-#include "base/hash.h"
-#include "base/message_loop/message_loop.h"
-#include "base/metrics/field_trial.h"
-#include "base/metrics/histogram.h"
-#include "base/rand_util.h"
-#include "base/strings/string_util.h"
-#include "base/strings/stringprintf.h"
-#include "base/sys_info.h"
-#include "base/threading/thread_restrictions.h"
-#include "base/time/time.h"
-#include "base/timer/timer.h"
-#include "net/base/net_errors.h"
-#include "net/disk_cache/blockfile/disk_format_v3.h"
-#include "net/disk_cache/blockfile/entry_impl_v3.h"
-#include "net/disk_cache/blockfile/errors.h"
-#include "net/disk_cache/blockfile/experiments.h"
-#include "net/disk_cache/blockfile/file.h"
-#include "net/disk_cache/blockfile/histogram_macros_v3.h"
-#include "net/disk_cache/blockfile/index_table_v3.h"
-#include "net/disk_cache/blockfile/storage_block-inl.h"
-#include "net/disk_cache/cache_util.h"
-
-// Provide a BackendImpl object to macros from histogram_macros.h.
-#define CACHE_UMA_BACKEND_IMPL_OBJ this
-
-using base::Time;
-using base::TimeDelta;
-using base::TimeTicks;
-
-namespace {
-
-#if defined(V3_NOT_JUST_YET_READY)
-const int kDefaultCacheSize = 80 * 1024 * 1024;
-
-// Avoid trimming the cache for the first 5 minutes (10 timer ticks).
-const int kTrimDelay = 10;
-#endif  // defined(V3_NOT_JUST_YET_READY).
-
-}  // namespace
-
-// ------------------------------------------------------------------------
-
-namespace disk_cache {
-
-BackendImplV3::BackendImplV3(
-    const base::FilePath& path,
-    const scoped_refptr<base::SingleThreadTaskRunner>& cache_thread,
-    net::NetLog* net_log)
-    : index_(NULL),
-      path_(path),
-      block_files_(),
-      max_size_(0),
-      up_ticks_(0),
-      cache_type_(net::DISK_CACHE),
-      uma_report_(0),
-      user_flags_(0),
-      init_(false),
-      restarted_(false),
-      read_only_(false),
-      disabled_(false),
-      lru_eviction_(true),
-      first_timer_(true),
-      user_load_(false),
-      net_log_(net_log),
-      ptr_factory_(this) {
-}
-
-BackendImplV3::~BackendImplV3() {
-  CleanupCache();
-}
-
-int BackendImplV3::Init(const CompletionCallback& callback) {
-  DCHECK(!init_);
-  if (init_)
-    return net::ERR_FAILED;
-
-  return net::ERR_IO_PENDING;
-}
-
-// ------------------------------------------------------------------------
-
-bool BackendImplV3::SetMaxSize(int max_bytes) {
-  static_assert(sizeof(max_bytes) == sizeof(max_size_),
-                "unsupported int model");
-  if (max_bytes < 0)
-    return false;
-
-  // Zero size means use the default.
-  if (!max_bytes)
-    return true;
-
-  // Avoid a DCHECK later on.
-  if (max_bytes >= kint32max - kint32max / 10)
-    max_bytes = kint32max - kint32max / 10 - 1;
-
-  user_flags_ |= MAX_SIZE;
-  max_size_ = max_bytes;
-  return true;
-}
-
-void BackendImplV3::SetType(net::CacheType type) {
-  DCHECK_NE(net::MEMORY_CACHE, type);
-  cache_type_ = type;
-}
-
-bool BackendImplV3::CreateBlock(FileType block_type, int block_count,
-                                Addr* block_address) {
-  return block_files_.CreateBlock(block_type, block_count, block_address);
-}
-
-#if defined(V3_NOT_JUST_YET_READY)
-void BackendImplV3::UpdateRank(EntryImplV3* entry, bool modified) {
-  if (read_only_ || (!modified && cache_type() == net::SHADER_CACHE))
-    return;
-  eviction_.UpdateRank(entry, modified);
-}
-
-void BackendImplV3::InternalDoomEntry(EntryImplV3* entry) {
-  uint32 hash = entry->GetHash();
-  std::string key = entry->GetKey();
-  Addr entry_addr = entry->entry()->address();
-  bool error;
-  EntryImpl* parent_entry = MatchEntry(key, hash, true, entry_addr, &error);
-  CacheAddr child(entry->GetNextAddress());
-
-  Trace("Doom entry 0x%p", entry);
-
-  if (!entry->doomed()) {
-    // We may have doomed this entry from within MatchEntry.
-    eviction_.OnDoomEntry(entry);
-    entry->InternalDoom();
-    if (!new_eviction_) {
-      DecreaseNumEntries();
-    }
-    stats_.OnEvent(Stats::DOOM_ENTRY);
-  }
-
-  if (parent_entry) {
-    parent_entry->SetNextAddress(Addr(child));
-    parent_entry->Release();
-  } else if (!error) {
-    data_->table[hash & mask_] = child;
-  }
-
-  FlushIndex();
-}
-
-void BackendImplV3::OnEntryDestroyBegin(Addr address) {
-  EntriesMap::iterator it = open_entries_.find(address.value());
-  if (it != open_entries_.end())
-    open_entries_.erase(it);
-}
-
-void BackendImplV3::OnEntryDestroyEnd() {
-  DecreaseNumRefs();
-  if (data_->header.num_bytes > max_size_ && !read_only_ &&
-      (up_ticks_ > kTrimDelay || user_flags_ & kNoRandom))
-    eviction_.TrimCache(false);
-}
-
-EntryImplV3* BackendImplV3::GetOpenEntry(Addr address) const {
-  DCHECK(rankings->HasData());
-  EntriesMap::const_iterator it =
-      open_entries_.find(rankings->Data()->contents);
-  if (it != open_entries_.end()) {
-    // We have this entry in memory.
-    return it->second;
-  }
-
-  return NULL;
-}
-
-int BackendImplV3::MaxFileSize() const {
-  return max_size_ / 8;
-}
-
-void BackendImplV3::ModifyStorageSize(int32 old_size, int32 new_size) {
-  if (disabled_ || old_size == new_size)
-    return;
-  if (old_size > new_size)
-    SubstractStorageSize(old_size - new_size);
-  else
-    AddStorageSize(new_size - old_size);
-
-  // Update the usage statistics.
-  stats_.ModifyStorageStats(old_size, new_size);
-}
-
-void BackendImplV3::TooMuchStorageRequested(int32 size) {
-  stats_.ModifyStorageStats(0, size);
-}
-
-bool BackendImplV3::IsAllocAllowed(int current_size, int new_size) {
-  DCHECK_GT(new_size, current_size);
-  if (user_flags_ & NO_BUFFERING)
-    return false;
-
-  int to_add = new_size - current_size;
-  if (buffer_bytes_ + to_add > MaxBuffersSize())
-    return false;
-
-  buffer_bytes_ += to_add;
-  CACHE_UMA(COUNTS_50000, "BufferBytes", buffer_bytes_ / 1024);
-  return true;
-}
-#endif  // defined(V3_NOT_JUST_YET_READY).
-
-void BackendImplV3::BufferDeleted(int size) {
-  DCHECK_GE(size, 0);
-  buffer_bytes_ -= size;
-  DCHECK_GE(buffer_bytes_, 0);
-}
-
-bool BackendImplV3::IsLoaded() const {
-  if (user_flags_ & NO_LOAD_PROTECTION)
-    return false;
-
-  return user_load_;
-}
-
-std::string BackendImplV3::HistogramName(const char* name) const {
-  static const char* const names[] = {
-    "Http", "", "Media", "AppCache", "Shader" };
-  DCHECK_NE(cache_type_, net::MEMORY_CACHE);
-  return base::StringPrintf("DiskCache3.%s_%s", name, names[cache_type_]);
-}
-
-base::WeakPtr<BackendImplV3> BackendImplV3::GetWeakPtr() {
-  return ptr_factory_.GetWeakPtr();
-}
-
-#if defined(V3_NOT_JUST_YET_READY)
-// We want to remove biases from some histograms so we only send data once per
-// week.
-bool BackendImplV3::ShouldReportAgain() {
-  if (uma_report_)
-    return uma_report_ == 2;
-
-  uma_report_++;
-  int64 last_report = stats_.GetCounter(Stats::LAST_REPORT);
-  Time last_time = Time::FromInternalValue(last_report);
-  if (!last_report || (Time::Now() - last_time).InDays() >= 7) {
-    stats_.SetCounter(Stats::LAST_REPORT, Time::Now().ToInternalValue());
-    uma_report_++;
-    return true;
-  }
-  return false;
-}
-
-void BackendImplV3::FirstEviction() {
-  IndexHeaderV3* header = index_.header();
-  header->flags |= CACHE_EVICTED;
-  DCHECK(header->create_time);
-  if (!GetEntryCount())
-    return;  // This is just for unit tests.
-
-  Time create_time = Time::FromInternalValue(header->create_time);
-  CACHE_UMA(AGE, "FillupAge", create_time);
-
-  int64 use_time = stats_.GetCounter(Stats::TIMER);
-  CACHE_UMA(HOURS, "FillupTime", static_cast<int>(use_time / 120));
-  CACHE_UMA(PERCENTAGE, "FirstHitRatio", stats_.GetHitRatio());
-
-  if (!use_time)
-    use_time = 1;
-  CACHE_UMA(COUNTS_10000, "FirstEntryAccessRate",
-            static_cast<int>(header->num_entries / use_time));
-  CACHE_UMA(COUNTS, "FirstByteIORate",
-            static_cast<int>((header->num_bytes / 1024) / use_time));
-
-  int avg_size = header->num_bytes / GetEntryCount();
-  CACHE_UMA(COUNTS, "FirstEntrySize", avg_size);
-
-  int large_entries_bytes = stats_.GetLargeEntriesSize();
-  int large_ratio = large_entries_bytes * 100 / header->num_bytes;
-  CACHE_UMA(PERCENTAGE, "FirstLargeEntriesRatio", large_ratio);
-
-  if (!lru_eviction_) {
-    CACHE_UMA(PERCENTAGE, "FirstResurrectRatio", stats_.GetResurrectRatio());
-    CACHE_UMA(PERCENTAGE, "FirstNoUseRatio",
-              header->num_no_use_entries * 100 / header->num_entries);
-    CACHE_UMA(PERCENTAGE, "FirstLowUseRatio",
-              header->num_low_use_entries * 100 / header->num_entries);
-    CACHE_UMA(PERCENTAGE, "FirstHighUseRatio",
-              header->num_high_use_entries * 100 / header->num_entries);
-  }
-
-  stats_.ResetRatios();
-}
-
-void BackendImplV3::OnEvent(Stats::Counters an_event) {
-  stats_.OnEvent(an_event);
-}
-
-void BackendImplV3::OnRead(int32 bytes) {
-  DCHECK_GE(bytes, 0);
-  byte_count_ += bytes;
-  if (byte_count_ < 0)
-    byte_count_ = kint32max;
-}
-
-void BackendImplV3::OnWrite(int32 bytes) {
-  // We use the same implementation as OnRead... just log the number of bytes.
-  OnRead(bytes);
-}
-
-void BackendImplV3::OnTimerTick() {
-  stats_.OnEvent(Stats::TIMER);
-  int64 time = stats_.GetCounter(Stats::TIMER);
-  int64 current = stats_.GetCounter(Stats::OPEN_ENTRIES);
-
-  // OPEN_ENTRIES is a sampled average of the number of open entries, avoiding
-  // the bias towards 0.
-  if (num_refs_ && (current != num_refs_)) {
-    int64 diff = (num_refs_ - current) / 50;
-    if (!diff)
-      diff = num_refs_ > current ? 1 : -1;
-    current = current + diff;
-    stats_.SetCounter(Stats::OPEN_ENTRIES, current);
-    stats_.SetCounter(Stats::MAX_ENTRIES, max_refs_);
-  }
-
-  CACHE_UMA(COUNTS, "NumberOfReferences", num_refs_);
-
-  CACHE_UMA(COUNTS_10000, "EntryAccessRate", entry_count_);
-  CACHE_UMA(COUNTS, "ByteIORate", byte_count_ / 1024);
-
-  // These values cover about 99.5% of the population (Oct 2011).
-  user_load_ = (entry_count_ > 300 || byte_count_ > 7 * 1024 * 1024);
-  entry_count_ = 0;
-  byte_count_ = 0;
-  up_ticks_++;
-
-  if (!data_)
-    first_timer_ = false;
-  if (first_timer_) {
-    first_timer_ = false;
-    if (ShouldReportAgain())
-      ReportStats();
-  }
-
-  // Save stats to disk at 5 min intervals.
-  if (time % 10 == 0)
-    StoreStats();
-}
-
-void BackendImplV3::SetUnitTestMode() {
-  user_flags_ |= UNIT_TEST_MODE;
-}
-
-void BackendImplV3::SetUpgradeMode() {
-  user_flags_ |= UPGRADE_MODE;
-  read_only_ = true;
-}
-
-void BackendImplV3::SetNewEviction() {
-  user_flags_ |= EVICTION_V2;
-  lru_eviction_ = false;
-}
-
-void BackendImplV3::SetFlags(uint32 flags) {
-  user_flags_ |= flags;
-}
-
-int BackendImplV3::FlushQueueForTest(const CompletionCallback& callback) {
-  background_queue_.FlushQueue(callback);
-  return net::ERR_IO_PENDING;
-}
-
-void BackendImplV3::TrimForTest(bool empty) {
-  eviction_.SetTestMode();
-  eviction_.TrimCache(empty);
-}
-
-void BackendImplV3::TrimDeletedListForTest(bool empty) {
-  eviction_.SetTestMode();
-  eviction_.TrimDeletedList(empty);
-}
-
-int BackendImplV3::SelfCheck() {
-  if (!init_) {
-    LOG(ERROR) << "Init failed";
-    return ERR_INIT_FAILED;
-  }
-
-  int num_entries = rankings_.SelfCheck();
-  if (num_entries < 0) {
-    LOG(ERROR) << "Invalid rankings list, error " << num_entries;
-#if !defined(NET_BUILD_STRESS_CACHE)
-    return num_entries;
-#endif
-  }
-
-  if (num_entries != data_->header.num_entries) {
-    LOG(ERROR) << "Number of entries mismatch";
-#if !defined(NET_BUILD_STRESS_CACHE)
-    return ERR_NUM_ENTRIES_MISMATCH;
-#endif
-  }
-
-  return CheckAllEntries();
-}
-
-// ------------------------------------------------------------------------
-
-net::CacheType BackendImplV3::GetCacheType() const {
-  return cache_type_;
-}
-
-int32 BackendImplV3::GetEntryCount() const {
-  if (disabled_)
-    return 0;
-  DCHECK(init_);
-  return index_.header()->num_entries;
-}
-
-int BackendImplV3::OpenEntry(const std::string& key, Entry** entry,
-                             const CompletionCallback& callback) {
-  if (disabled_)
-    return NULL;
-
-  TimeTicks start = TimeTicks::Now();
-  uint32 hash = base::Hash(key);
-  Trace("Open hash 0x%x", hash);
-
-  bool error;
-  EntryImpl* cache_entry = MatchEntry(key, hash, false, Addr(), &error);
-  if (cache_entry && ENTRY_NORMAL != cache_entry->entry()->Data()->state) {
-    // The entry was already evicted.
-    cache_entry->Release();
-    cache_entry = NULL;
-  }
-
-  int current_size = data_->header.num_bytes / (1024 * 1024);
-  int64 total_hours = stats_.GetCounter(Stats::TIMER) / 120;
-  int64 no_use_hours = stats_.GetCounter(Stats::LAST_REPORT_TIMER) / 120;
-  int64 use_hours = total_hours - no_use_hours;
-
-  if (!cache_entry) {
-    CACHE_UMA(AGE_MS, "OpenTime.Miss", 0, start);
-    CACHE_UMA(COUNTS_10000, "AllOpenBySize.Miss", 0, current_size);
-    CACHE_UMA(HOURS, "AllOpenByTotalHours.Miss", 0, total_hours);
-    CACHE_UMA(HOURS, "AllOpenByUseHours.Miss", 0, use_hours);
-    stats_.OnEvent(Stats::OPEN_MISS);
-    return NULL;
-  }
-
-  eviction_.OnOpenEntry(cache_entry);
-  entry_count_++;
-
-  Trace("Open hash 0x%x end: 0x%x", hash,
-        cache_entry->entry()->address().value());
-  CACHE_UMA(AGE_MS, "OpenTime", 0, start);
-  CACHE_UMA(COUNTS_10000, "AllOpenBySize.Hit", 0, current_size);
-  CACHE_UMA(HOURS, "AllOpenByTotalHours.Hit", 0, total_hours);
-  CACHE_UMA(HOURS, "AllOpenByUseHours.Hit", 0, use_hours);
-  stats_.OnEvent(Stats::OPEN_HIT);
-  SIMPLE_STATS_COUNTER("disk_cache.hit");
-  return cache_entry;
-}
-
-int BackendImplV3::CreateEntry(const std::string& key, Entry** entry,
-                               const CompletionCallback& callback) {
-  if (disabled_ || key.empty())
-    return NULL;
-
-  TimeTicks start = TimeTicks::Now();
-  Trace("Create hash 0x%x", hash);
-
-  scoped_refptr<EntryImpl> parent;
-  Addr entry_address(data_->table[hash & mask_]);
-  if (entry_address.is_initialized()) {
-    // We have an entry already. It could be the one we are looking for, or just
-    // a hash conflict.
-    bool error;
-    EntryImpl* old_entry = MatchEntry(key, hash, false, Addr(), &error);
-    if (old_entry)
-      return ResurrectEntry(old_entry);
-
-    EntryImpl* parent_entry = MatchEntry(key, hash, true, Addr(), &error);
-    DCHECK(!error);
-    if (parent_entry) {
-      parent.swap(&parent_entry);
-    } else if (data_->table[hash & mask_]) {
-      // We should have corrected the problem.
-      NOTREACHED();
-      return NULL;
-    }
-  }
-
-  // The general flow is to allocate disk space and initialize the entry data,
-  // followed by saving that to disk, then linking the entry though the index
-  // and finally through the lists. If there is a crash in this process, we may
-  // end up with:
-  // a. Used, unreferenced empty blocks on disk (basically just garbage).
-  // b. Used, unreferenced but meaningful data on disk (more garbage).
-  // c. A fully formed entry, reachable only through the index.
-  // d. A fully formed entry, also reachable through the lists, but still dirty.
-  //
-  // Anything after (b) can be automatically cleaned up. We may consider saving
-  // the current operation (as we do while manipulating the lists) so that we
-  // can detect and cleanup (a) and (b).
-
-  int num_blocks = EntryImpl::NumBlocksForEntry(key.size());
-  if (!block_files_.CreateBlock(BLOCK_256, num_blocks, &entry_address)) {
-    LOG(ERROR) << "Create entry failed " << key.c_str();
-    stats_.OnEvent(Stats::CREATE_ERROR);
-    return NULL;
-  }
-
-  Addr node_address(0);
-  if (!block_files_.CreateBlock(RANKINGS, 1, &node_address)) {
-    block_files_.DeleteBlock(entry_address, false);
-    LOG(ERROR) << "Create entry failed " << key.c_str();
-    stats_.OnEvent(Stats::CREATE_ERROR);
-    return NULL;
-  }
-
-  scoped_refptr<EntryImpl> cache_entry(
-      new EntryImpl(this, entry_address, false));
-  IncreaseNumRefs();
-
-  if (!cache_entry->CreateEntry(node_address, key, hash)) {
-    block_files_.DeleteBlock(entry_address, false);
-    block_files_.DeleteBlock(node_address, false);
-    LOG(ERROR) << "Create entry failed " << key.c_str();
-    stats_.OnEvent(Stats::CREATE_ERROR);
-    return NULL;
-  }
-
-  cache_entry->BeginLogging(net_log_, true);
-
-  // We are not failing the operation; let's add this to the map.
-  open_entries_[entry_address.value()] = cache_entry.get();
-
-  // Save the entry.
-  cache_entry->entry()->Store();
-  cache_entry->rankings()->Store();
-  IncreaseNumEntries();
-  entry_count_++;
-
-  // Link this entry through the index.
-  if (parent.get()) {
-    parent->SetNextAddress(entry_address);
-  } else {
-    data_->table[hash & mask_] = entry_address.value();
-  }
-
-  // Link this entry through the lists.
-  eviction_.OnCreateEntry(cache_entry.get());
-
-  CACHE_UMA(AGE_MS, "CreateTime", 0, start);
-  stats_.OnEvent(Stats::CREATE_HIT);
-  SIMPLE_STATS_COUNTER("disk_cache.miss");
-  Trace("create entry hit ");
-  FlushIndex();
-  cache_entry->AddRef();
-  return cache_entry.get();
-}
-
-int BackendImplV3::DoomEntry(const std::string& key,
-                             const CompletionCallback& callback) {
-  if (disabled_)
-    return net::ERR_FAILED;
-
-  EntryImpl* entry = OpenEntryImpl(key);
-  if (!entry)
-    return net::ERR_FAILED;
-
-  entry->DoomImpl();
-  entry->Release();
-  return net::OK;
-}
-
-int BackendImplV3::DoomAllEntries(const CompletionCallback& callback) {
-  // This is not really an error, but it is an interesting condition.
-  ReportError(ERR_CACHE_DOOMED);
-  stats_.OnEvent(Stats::DOOM_CACHE);
-  if (!num_refs_) {
-    RestartCache(false);
-    return disabled_ ? net::ERR_FAILED : net::OK;
-  } else {
-    if (disabled_)
-      return net::ERR_FAILED;
-
-    eviction_.TrimCache(true);
-    return net::OK;
-  }
-}
-
-int BackendImplV3::DoomEntriesBetween(base::Time initial_time,
-                                      base::Time end_time,
-                                      const CompletionCallback& callback) {
-  DCHECK_NE(net::APP_CACHE, cache_type_);
-  if (end_time.is_null())
-    return SyncDoomEntriesSince(initial_time);
-
-  DCHECK(end_time >= initial_time);
-
-  if (disabled_)
-    return net::ERR_FAILED;
-
-  EntryImpl* node;
-  void* iter = NULL;
-  EntryImpl* next = OpenNextEntryImpl(&iter);
-  if (!next)
-    return net::OK;
-
-  while (next) {
-    node = next;
-    next = OpenNextEntryImpl(&iter);
-
-    if (node->GetLastUsed() >= initial_time &&
-        node->GetLastUsed() < end_time) {
-      node->DoomImpl();
-    } else if (node->GetLastUsed() < initial_time) {
-      if (next)
-        next->Release();
-      next = NULL;
-      SyncEndEnumeration(iter);
-    }
-
-    node->Release();
-  }
-
-  return net::OK;
-}
-
-int BackendImplV3::DoomEntriesSince(base::Time initial_time,
-                                    const CompletionCallback& callback) {
-  DCHECK_NE(net::APP_CACHE, cache_type_);
-  if (disabled_)
-    return net::ERR_FAILED;
-
-  stats_.OnEvent(Stats::DOOM_RECENT);
-  for (;;) {
-    void* iter = NULL;
-    EntryImpl* entry = OpenNextEntryImpl(&iter);
-    if (!entry)
-      return net::OK;
-
-    if (initial_time > entry->GetLastUsed()) {
-      entry->Release();
-      SyncEndEnumeration(iter);
-      return net::OK;
-    }
-
-    entry->DoomImpl();
-    entry->Release();
-    SyncEndEnumeration(iter);  // Dooming the entry invalidates the iterator.
-  }
-}
-
-class BackendImplV3::IteratorImpl : public Backend::Iterator {
- public:
-  explicit IteratorImpl(base::WeakPtr<InFlightBackendIO> background_queue)
-      : background_queue_(background_queue), data_(NULL) {
-  }
-
-  virtual int OpenNextEntry(Entry** next_entry,
-                            const net::CompletionCallback& callback) override {
-    if (!background_queue_)
-      return net::ERR_FAILED;
-    background_queue_->OpenNextEntry(&data_, next_entry, callback);
-    return net::ERR_IO_PENDING;
-  }
-
- private:
-  const base::WeakPtr<InFlightBackendIO> background_queue_;
-  void* data_;
-};
-
-scoped_ptr<Backend::Iterator> BackendImplV3::CreateIterator() {
-  return scoped_ptr<Backend::Iterator>(new IteratorImpl(GetBackgroundQueue()));
-}
-
-void BackendImplV3::GetStats(StatsItems* stats) {
-  if (disabled_)
-    return;
-
-  std::pair<std::string, std::string> item;
-
-  item.first = "Entries";
-  item.second = base::StringPrintf("%d", data_->header.num_entries);
-  stats->push_back(item);
-
-  item.first = "Pending IO";
-  item.second = base::StringPrintf("%d", num_pending_io_);
-  stats->push_back(item);
-
-  item.first = "Max size";
-  item.second = base::StringPrintf("%d", max_size_);
-  stats->push_back(item);
-
-  item.first = "Current size";
-  item.second = base::StringPrintf("%d", data_->header.num_bytes);
-  stats->push_back(item);
-
-  item.first = "Cache type";
-  item.second = "Blockfile Cache";
-  stats->push_back(item);
-
-  stats_.GetItems(stats);
-}
-
-void BackendImplV3::OnExternalCacheHit(const std::string& key) {
-  if (disabled_)
-    return;
-
-  uint32 hash = base::Hash(key);
-  bool error;
-  EntryImpl* cache_entry = MatchEntry(key, hash, false, Addr(), &error);
-  if (cache_entry) {
-    if (ENTRY_NORMAL == cache_entry->entry()->Data()->state) {
-      UpdateRank(cache_entry, cache_type() == net::SHADER_CACHE);
-    }
-    cache_entry->Release();
-  }
-}
-
-// ------------------------------------------------------------------------
-
-// The maximum cache size will be either set explicitly by the caller, or
-// calculated by this code.
-void BackendImplV3::AdjustMaxCacheSize(int table_len) {
-  if (max_size_)
-    return;
-
-  // If table_len is provided, the index file exists.
-  DCHECK(!table_len || data_->header.magic);
-
-  // The user is not setting the size, let's figure it out.
-  int64 available = base::SysInfo::AmountOfFreeDiskSpace(path_);
-  if (available < 0) {
-    max_size_ = kDefaultCacheSize;
-    return;
-  }
-
-  if (table_len)
-    available += data_->header.num_bytes;
-
-  max_size_ = PreferedCacheSize(available);
-
-  // Let's not use more than the default size while we tune-up the performance
-  // of bigger caches. TODO(rvargas): remove this limit.
-  if (max_size_ > kDefaultCacheSize * 4)
-    max_size_ = kDefaultCacheSize * 4;
-
-  if (!table_len)
-    return;
-
-  // If we already have a table, adjust the size to it.
-  int current_max_size = MaxStorageSizeForTable(table_len);
-  if (max_size_ > current_max_size)
-    max_size_= current_max_size;
-}
-
-bool BackendImplV3::InitStats() {
-  Addr address(data_->header.stats);
-  int size = stats_.StorageSize();
-
-  if (!address.is_initialized()) {
-    FileType file_type = Addr::RequiredFileType(size);
-    DCHECK_NE(file_type, EXTERNAL);
-    int num_blocks = Addr::RequiredBlocks(size, file_type);
-
-    if (!CreateBlock(file_type, num_blocks, &address))
-      return false;
-    return stats_.Init(NULL, 0, address);
-  }
-
-  if (!address.is_block_file()) {
-    NOTREACHED();
-    return false;
-  }
-
-  // Load the required data.
-  size = address.num_blocks() * address.BlockSize();
-  MappedFile* file = File(address);
-  if (!file)
-    return false;
-
-  scoped_ptr<char[]> data(new char[size]);
-  size_t offset = address.start_block() * address.BlockSize() +
-                  kBlockHeaderSize;
-  if (!file->Read(data.get(), size, offset))
-    return false;
-
-  if (!stats_.Init(data.get(), size, address))
-    return false;
-  if (cache_type_ == net::DISK_CACHE && ShouldReportAgain())
-    stats_.InitSizeHistogram();
-  return true;
-}
-
-void BackendImplV3::StoreStats() {
-  int size = stats_.StorageSize();
-  scoped_ptr<char[]> data(new char[size]);
-  Addr address;
-  size = stats_.SerializeStats(data.get(), size, &address);
-  DCHECK(size);
-  if (!address.is_initialized())
-    return;
-
-  MappedFile* file = File(address);
-  if (!file)
-    return;
-
-  size_t offset = address.start_block() * address.BlockSize() +
-                  kBlockHeaderSize;
-  file->Write(data.get(), size, offset);  // ignore result.
-}
-
-void BackendImplV3::RestartCache(bool failure) {
-  int64 errors = stats_.GetCounter(Stats::FATAL_ERROR);
-  int64 full_dooms = stats_.GetCounter(Stats::DOOM_CACHE);
-  int64 partial_dooms = stats_.GetCounter(Stats::DOOM_RECENT);
-  int64 last_report = stats_.GetCounter(Stats::LAST_REPORT);
-
-  PrepareForRestart();
-  if (failure) {
-    DCHECK(!num_refs_);
-    DCHECK(!open_entries_.size());
-    DelayedCacheCleanup(path_);
-  } else {
-    DeleteCache(path_, false);
-  }
-
-  // Don't call Init() if directed by the unit test: we are simulating a failure
-  // trying to re-enable the cache.
-  if (unit_test_)
-    init_ = true;  // Let the destructor do proper cleanup.
-  else if (SyncInit() == net::OK) {
-    stats_.SetCounter(Stats::FATAL_ERROR, errors);
-    stats_.SetCounter(Stats::DOOM_CACHE, full_dooms);
-    stats_.SetCounter(Stats::DOOM_RECENT, partial_dooms);
-    stats_.SetCounter(Stats::LAST_REPORT, last_report);
-  }
-}
-
-void BackendImplV3::PrepareForRestart() {
-  if (!(user_flags_ & EVICTION_V2))
-    lru_eviction_ = true;
-
-  disabled_ = true;
-  data_->header.crash = 0;
-  index_->Flush();
-  index_ = NULL;
-  data_ = NULL;
-  block_files_.CloseFiles();
-  rankings_.Reset();
-  init_ = false;
-  restarted_ = true;
-}
-
-void BackendImplV3::CleanupCache() {
-  Trace("Backend Cleanup");
-  eviction_.Stop();
-  timer_.reset();
-
-  if (init_) {
-    StoreStats();
-    if (data_)
-      data_->header.crash = 0;
-
-    if (user_flags_ & kNoRandom) {
-      // This is a net_unittest, verify that we are not 'leaking' entries.
-      File::WaitForPendingIO(&num_pending_io_);
-      DCHECK(!num_refs_);
-    } else {
-      File::DropPendingIO();
-    }
-  }
-  block_files_.CloseFiles();
-  FlushIndex();
-  index_ = NULL;
-  ptr_factory_.InvalidateWeakPtrs();
-  done_.Signal();
-}
-
-int BackendImplV3::NewEntry(Addr address, EntryImplV3** entry) {
-  EntriesMap::iterator it = open_entries_.find(address.value());
-  if (it != open_entries_.end()) {
-    // Easy job. This entry is already in memory.
-    EntryImpl* this_entry = it->second;
-    this_entry->AddRef();
-    *entry = this_entry;
-    return 0;
-  }
-
-  STRESS_DCHECK(block_files_.IsValid(address));
-
-  if (!address.SanityCheckForEntry()) {
-    LOG(WARNING) << "Wrong entry address.";
-    STRESS_NOTREACHED();
-    return ERR_INVALID_ADDRESS;
-  }
-
-  scoped_refptr<EntryImpl> cache_entry(
-      new EntryImpl(this, address, read_only_));
-  IncreaseNumRefs();
-  *entry = NULL;
-
-  TimeTicks start = TimeTicks::Now();
-  if (!cache_entry->entry()->Load())
-    return ERR_READ_FAILURE;
-
-  if (IsLoaded()) {
-    CACHE_UMA(AGE_MS, "LoadTime", 0, start);
-  }
-
-  if (!cache_entry->SanityCheck()) {
-    LOG(WARNING) << "Messed up entry found.";
-    STRESS_NOTREACHED();
-    return ERR_INVALID_ENTRY;
-  }
-
-  STRESS_DCHECK(block_files_.IsValid(
-                    Addr(cache_entry->entry()->Data()->rankings_node)));
-
-  if (!cache_entry->LoadNodeAddress())
-    return ERR_READ_FAILURE;
-
-  if (!rankings_.SanityCheck(cache_entry->rankings(), false)) {
-    STRESS_NOTREACHED();
-    cache_entry->SetDirtyFlag(0);
-    // Don't remove this from the list (it is not linked properly). Instead,
-    // break the link back to the entry because it is going away, and leave the
-    // rankings node to be deleted if we find it through a list.
-    rankings_.SetContents(cache_entry->rankings(), 0);
-  } else if (!rankings_.DataSanityCheck(cache_entry->rankings(), false)) {
-    STRESS_NOTREACHED();
-    cache_entry->SetDirtyFlag(0);
-    rankings_.SetContents(cache_entry->rankings(), address.value());
-  }
-
-  if (!cache_entry->DataSanityCheck()) {
-    LOG(WARNING) << "Messed up entry found.";
-    cache_entry->SetDirtyFlag(0);
-    cache_entry->FixForDelete();
-  }
-
-  // Prevent overwriting the dirty flag on the destructor.
-  cache_entry->SetDirtyFlag(GetCurrentEntryId());
-
-  if (cache_entry->dirty()) {
-    Trace("Dirty entry 0x%p 0x%x", reinterpret_cast<void*>(cache_entry.get()),
-          address.value());
-  }
-
-  open_entries_[address.value()] = cache_entry.get();
-
-  cache_entry->BeginLogging(net_log_, false);
-  cache_entry.swap(entry);
-  return 0;
-}
-
-void BackendImplV3::AddStorageSize(int32 bytes) {
-  data_->header.num_bytes += bytes;
-  DCHECK_GE(data_->header.num_bytes, 0);
-}
-
-void BackendImplV3::SubstractStorageSize(int32 bytes) {
-  data_->header.num_bytes -= bytes;
-  DCHECK_GE(data_->header.num_bytes, 0);
-}
-
-void BackendImplV3::IncreaseNumRefs() {
-  num_refs_++;
-  if (max_refs_ < num_refs_)
-    max_refs_ = num_refs_;
-}
-
-void BackendImplV3::DecreaseNumRefs() {
-  DCHECK(num_refs_);
-  num_refs_--;
-
-  if (!num_refs_ && disabled_)
-    base::MessageLoop::current()->PostTask(
-        FROM_HERE, base::Bind(&BackendImpl::RestartCache, GetWeakPtr(), true));
-}
-
-void BackendImplV3::IncreaseNumEntries() {
-  index_.header()->num_entries++;
-  DCHECK_GT(index_.header()->num_entries, 0);
-}
-
-void BackendImplV3::DecreaseNumEntries() {
-  index_.header()->num_entries--;
-  if (index_.header()->num_entries < 0) {
-    NOTREACHED();
-    index_.header()->num_entries = 0;
-  }
-}
-
-int BackendImplV3::SyncInit() {
-#if defined(NET_BUILD_STRESS_CACHE)
-  // Start evictions right away.
-  up_ticks_ = kTrimDelay * 2;
-#endif
-  DCHECK(!init_);
-  if (init_)
-    return net::ERR_FAILED;
-
-  bool create_files = false;
-  if (!InitBackingStore(&create_files)) {
-    ReportError(ERR_STORAGE_ERROR);
-    return net::ERR_FAILED;
-  }
-
-  num_refs_ = num_pending_io_ = max_refs_ = 0;
-  entry_count_ = byte_count_ = 0;
-
-  if (!restarted_) {
-    buffer_bytes_ = 0;
-    trace_object_ = TraceObject::GetTraceObject();
-    // Create a recurrent timer of 30 secs.
-    int timer_delay = unit_test_ ? 1000 : 30000;
-    timer_.reset(new base::RepeatingTimer<BackendImplV3>());
-    timer_->Start(FROM_HERE, TimeDelta::FromMilliseconds(timer_delay), this,
-                  &BackendImplV3::OnStatsTimer);
-  }
-
-  init_ = true;
-  Trace("Init");
-
-  if (data_->header.experiment != NO_EXPERIMENT &&
-      cache_type_ != net::DISK_CACHE) {
-    // No experiment for other caches.
-    return net::ERR_FAILED;
-  }
-
-  if (!(user_flags_ & kNoRandom)) {
-    // The unit test controls directly what to test.
-    new_eviction_ = (cache_type_ == net::DISK_CACHE);
-  }
-
-  if (!CheckIndex()) {
-    ReportError(ERR_INIT_FAILED);
-    return net::ERR_FAILED;
-  }
-
-  if (!restarted_ && (create_files || !data_->header.num_entries))
-    ReportError(ERR_CACHE_CREATED);
-
-  if (!(user_flags_ & kNoRandom) && cache_type_ == net::DISK_CACHE &&
-      !InitExperiment(&data_->header, create_files)) {
-    return net::ERR_FAILED;
-  }
-
-  // We don't care if the value overflows. The only thing we care about is that
-  // the id cannot be zero, because that value is used as "not dirty".
-  // Increasing the value once per second gives us many years before we start
-  // having collisions.
-  data_->header.this_id++;
-  if (!data_->header.this_id)
-    data_->header.this_id++;
-
-  bool previous_crash = (data_->header.crash != 0);
-  data_->header.crash = 1;
-
-  if (!block_files_.Init(create_files))
-    return net::ERR_FAILED;
-
-  // We want to minimize the changes to cache for an AppCache.
-  if (cache_type() == net::APP_CACHE) {
-    DCHECK(!new_eviction_);
-    read_only_ = true;
-  } else if (cache_type() == net::SHADER_CACHE) {
-    DCHECK(!new_eviction_);
-  }
-
-  eviction_.Init(this);
-
-  // stats_ and rankings_ may end up calling back to us so we better be enabled.
-  disabled_ = false;
-  if (!InitStats())
-    return net::ERR_FAILED;
-
-  disabled_ = !rankings_.Init(this, new_eviction_);
-
-#if defined(STRESS_CACHE_EXTENDED_VALIDATION)
-  trace_object_->EnableTracing(false);
-  int sc = SelfCheck();
-  if (sc < 0 && sc != ERR_NUM_ENTRIES_MISMATCH)
-    NOTREACHED();
-  trace_object_->EnableTracing(true);
-#endif
-
-  if (previous_crash) {
-    ReportError(ERR_PREVIOUS_CRASH);
-  } else if (!restarted_) {
-    ReportError(ERR_NO_ERROR);
-  }
-
-  FlushIndex();
-
-  return disabled_ ? net::ERR_FAILED : net::OK;
-}
-
-EntryImpl* BackendImplV3::ResurrectEntry(EntryImpl* deleted_entry) {
-  if (ENTRY_NORMAL == deleted_entry->entry()->Data()->state) {
-    deleted_entry->Release();
-    stats_.OnEvent(Stats::CREATE_MISS);
-    Trace("create entry miss ");
-    return NULL;
-  }
-
-  // We are attempting to create an entry and found out that the entry was
-  // previously deleted.
-
-  eviction_.OnCreateEntry(deleted_entry);
-  entry_count_++;
-
-  stats_.OnEvent(Stats::RESURRECT_HIT);
-  Trace("Resurrect entry hit ");
-  return deleted_entry;
-}
-
-EntryImpl* BackendImplV3::CreateEntryImpl(const std::string& key) {
-  if (disabled_ || key.empty())
-    return NULL;
-
-  TimeTicks start = TimeTicks::Now();
-  Trace("Create hash 0x%x", hash);
-
-  scoped_refptr<EntryImpl> parent;
-  Addr entry_address(data_->table[hash & mask_]);
-  if (entry_address.is_initialized()) {
-    // We have an entry already. It could be the one we are looking for, or just
-    // a hash conflict.
-    bool error;
-    EntryImpl* old_entry = MatchEntry(key, hash, false, Addr(), &error);
-    if (old_entry)
-      return ResurrectEntry(old_entry);
-
-    EntryImpl* parent_entry = MatchEntry(key, hash, true, Addr(), &error);
-    DCHECK(!error);
-    if (parent_entry) {
-      parent.swap(&parent_entry);
-    } else if (data_->table[hash & mask_]) {
-      // We should have corrected the problem.
-      NOTREACHED();
-      return NULL;
-    }
-  }
-
-  // The general flow is to allocate disk space and initialize the entry data,
-  // followed by saving that to disk, then linking the entry though the index
-  // and finally through the lists. If there is a crash in this process, we may
-  // end up with:
-  // a. Used, unreferenced empty blocks on disk (basically just garbage).
-  // b. Used, unreferenced but meaningful data on disk (more garbage).
-  // c. A fully formed entry, reachable only through the index.
-  // d. A fully formed entry, also reachable through the lists, but still dirty.
-  //
-  // Anything after (b) can be automatically cleaned up. We may consider saving
-  // the current operation (as we do while manipulating the lists) so that we
-  // can detect and cleanup (a) and (b).
-
-  int num_blocks = EntryImpl::NumBlocksForEntry(key.size());
-  if (!block_files_.CreateBlock(BLOCK_256, num_blocks, &entry_address)) {
-    LOG(ERROR) << "Create entry failed " << key.c_str();
-    stats_.OnEvent(Stats::CREATE_ERROR);
-    return NULL;
-  }
-
-  Addr node_address(0);
-  if (!block_files_.CreateBlock(RANKINGS, 1, &node_address)) {
-    block_files_.DeleteBlock(entry_address, false);
-    LOG(ERROR) << "Create entry failed " << key.c_str();
-    stats_.OnEvent(Stats::CREATE_ERROR);
-    return NULL;
-  }
-
-  scoped_refptr<EntryImpl> cache_entry(
-      new EntryImpl(this, entry_address, false));
-  IncreaseNumRefs();
-
-  if (!cache_entry->CreateEntry(node_address, key, hash)) {
-    block_files_.DeleteBlock(entry_address, false);
-    block_files_.DeleteBlock(node_address, false);
-    LOG(ERROR) << "Create entry failed " << key.c_str();
-    stats_.OnEvent(Stats::CREATE_ERROR);
-    return NULL;
-  }
-
-  cache_entry->BeginLogging(net_log_, true);
-
-  // We are not failing the operation; let's add this to the map.
-  open_entries_[entry_address.value()] = cache_entry;
-
-  // Save the entry.
-  cache_entry->entry()->Store();
-  cache_entry->rankings()->Store();
-  IncreaseNumEntries();
-  entry_count_++;
-
-  // Link this entry through the index.
-  if (parent.get()) {
-    parent->SetNextAddress(entry_address);
-  } else {
-    data_->table[hash & mask_] = entry_address.value();
-  }
-
-  // Link this entry through the lists.
-  eviction_.OnCreateEntry(cache_entry);
-
-  CACHE_UMA(AGE_MS, "CreateTime", 0, start);
-  stats_.OnEvent(Stats::CREATE_HIT);
-  SIMPLE_STATS_COUNTER("disk_cache.miss");
-  Trace("create entry hit ");
-  FlushIndex();
-  cache_entry->AddRef();
-  return cache_entry.get();
-}
-
-void BackendImplV3::LogStats() {
-  StatsItems stats;
-  GetStats(&stats);
-
-  for (size_t index = 0; index < stats.size(); index++)
-    VLOG(1) << stats[index].first << ": " << stats[index].second;
-}
-
-void BackendImplV3::ReportStats() {
-  IndexHeaderV3* header = index_.header();
-  CACHE_UMA(COUNTS, "Entries", header->num_entries);
-
-  int current_size = header->num_bytes / (1024 * 1024);
-  int max_size = max_size_ / (1024 * 1024);
-
-  CACHE_UMA(COUNTS_10000, "Size", current_size);
-  CACHE_UMA(COUNTS_10000, "MaxSize", max_size);
-  if (!max_size)
-    max_size++;
-  CACHE_UMA(PERCENTAGE, "UsedSpace", current_size * 100 / max_size);
-
-  CACHE_UMA(COUNTS_10000, "AverageOpenEntries",
-            static_cast<int>(stats_.GetCounter(Stats::OPEN_ENTRIES)));
-  CACHE_UMA(COUNTS_10000, "MaxOpenEntries",
-            static_cast<int>(stats_.GetCounter(Stats::MAX_ENTRIES)));
-  stats_.SetCounter(Stats::MAX_ENTRIES, 0);
-
-  CACHE_UMA(COUNTS_10000, "TotalFatalErrors",
-            static_cast<int>(stats_.GetCounter(Stats::FATAL_ERROR)));
-  CACHE_UMA(COUNTS_10000, "TotalDoomCache",
-            static_cast<int>(stats_.GetCounter(Stats::DOOM_CACHE)));
-  CACHE_UMA(COUNTS_10000, "TotalDoomRecentEntries",
-            static_cast<int>(stats_.GetCounter(Stats::DOOM_RECENT)));
-  stats_.SetCounter(Stats::FATAL_ERROR, 0);
-  stats_.SetCounter(Stats::DOOM_CACHE, 0);
-  stats_.SetCounter(Stats::DOOM_RECENT, 0);
-
-  int64 total_hours = stats_.GetCounter(Stats::TIMER) / 120;
-  if (!(header->flags & CACHE_EVICTED)) {
-    CACHE_UMA(HOURS, "TotalTimeNotFull", static_cast<int>(total_hours));
-    return;
-  }
-
-  // This is an up to date client that will report FirstEviction() data. After
-  // that event, start reporting this:
-
-  CACHE_UMA(HOURS, "TotalTime", static_cast<int>(total_hours));
-
-  int64 use_hours = stats_.GetCounter(Stats::LAST_REPORT_TIMER) / 120;
-  stats_.SetCounter(Stats::LAST_REPORT_TIMER, stats_.GetCounter(Stats::TIMER));
-
-  // We may see users with no use_hours at this point if this is the first time
-  // we are running this code.
-  if (use_hours)
-    use_hours = total_hours - use_hours;
-
-  if (!use_hours || !GetEntryCount() || !header->num_bytes)
-    return;
-
-  CACHE_UMA(HOURS, "UseTime", static_cast<int>(use_hours));
-
-  int64 trim_rate = stats_.GetCounter(Stats::TRIM_ENTRY) / use_hours;
-  CACHE_UMA(COUNTS, "TrimRate", static_cast<int>(trim_rate));
-
-  int avg_size = header->num_bytes / GetEntryCount();
-  CACHE_UMA(COUNTS, "EntrySize", avg_size);
-  CACHE_UMA(COUNTS, "EntriesFull", header->num_entries);
-
-  int large_entries_bytes = stats_.GetLargeEntriesSize();
-  int large_ratio = large_entries_bytes * 100 / header->num_bytes;
-  CACHE_UMA(PERCENTAGE, "LargeEntriesRatio", large_ratio);
-
-  if (!lru_eviction_) {
-    CACHE_UMA(PERCENTAGE, "ResurrectRatio", stats_.GetResurrectRatio());
-    CACHE_UMA(PERCENTAGE, "NoUseRatio",
-              header->num_no_use_entries * 100 / header->num_entries);
-    CACHE_UMA(PERCENTAGE, "LowUseRatio",
-              header->num_low_use_entries * 100 / header->num_entries);
-    CACHE_UMA(PERCENTAGE, "HighUseRatio",
-              header->num_high_use_entries * 100 / header->num_entries);
-    CACHE_UMA(PERCENTAGE, "DeletedRatio",
-              header->num_evicted_entries * 100 / header->num_entries);
-  }
-
-  stats_.ResetRatios();
-  stats_.SetCounter(Stats::TRIM_ENTRY, 0);
-
-  if (cache_type_ == net::DISK_CACHE)
-    block_files_.ReportStats();
-}
-
-void BackendImplV3::ReportError(int error) {
-  STRESS_DCHECK(!error || error == ERR_PREVIOUS_CRASH ||
-                error == ERR_CACHE_CREATED);
-
-  // We transmit positive numbers, instead of direct error codes.
-  DCHECK_LE(error, 0);
-  CACHE_UMA(CACHE_ERROR, "Error", error * -1);
-}
-
-bool BackendImplV3::CheckIndex() {
-  DCHECK(data_);
-
-  size_t current_size = index_->GetLength();
-  if (current_size < sizeof(Index)) {
-    LOG(ERROR) << "Corrupt Index file";
-    return false;
-  }
-
-  if (new_eviction_) {
-    // We support versions 2.0 and 2.1, upgrading 2.0 to 2.1.
-    if (kIndexMagic != data_->header.magic ||
-        kCurrentVersion >> 16 != data_->header.version >> 16) {
-      LOG(ERROR) << "Invalid file version or magic";
-      return false;
-    }
-    if (kCurrentVersion == data_->header.version) {
-      // We need file version 2.1 for the new eviction algorithm.
-      UpgradeTo2_1();
-    }
-  } else {
-    if (kIndexMagic != data_->header.magic ||
-        kCurrentVersion != data_->header.version) {
-      LOG(ERROR) << "Invalid file version or magic";
-      return false;
-    }
-  }
-
-  if (!data_->header.table_len) {
-    LOG(ERROR) << "Invalid table size";
-    return false;
-  }
-
-  if (current_size < GetIndexSize(data_->header.table_len) ||
-      data_->header.table_len & (kBaseTableLen - 1)) {
-    LOG(ERROR) << "Corrupt Index file";
-    return false;
-  }
-
-  AdjustMaxCacheSize(data_->header.table_len);
-
-#if !defined(NET_BUILD_STRESS_CACHE)
-  if (data_->header.num_bytes < 0 ||
-      (max_size_ < kint32max - kDefaultCacheSize &&
-       data_->header.num_bytes > max_size_ + kDefaultCacheSize)) {
-    LOG(ERROR) << "Invalid cache (current) size";
-    return false;
-  }
-#endif
-
-  if (data_->header.num_entries < 0) {
-    LOG(ERROR) << "Invalid number of entries";
-    return false;
-  }
-
-  if (!mask_)
-    mask_ = data_->header.table_len - 1;
-
-  // Load the table into memory with a single read.
-  scoped_ptr<char[]> buf(new char[current_size]);
-  return index_->Read(buf.get(), current_size, 0);
-}
-
-int BackendImplV3::CheckAllEntries() {
-  int num_dirty = 0;
-  int num_entries = 0;
-  DCHECK(mask_ < kuint32max);
-  for (unsigned int i = 0; i <= mask_; i++) {
-    Addr address(data_->table[i]);
-    if (!address.is_initialized())
-      continue;
-    for (;;) {
-      EntryImpl* tmp;
-      int ret = NewEntry(address, &tmp);
-      if (ret) {
-        STRESS_NOTREACHED();
-        return ret;
-      }
-      scoped_refptr<EntryImpl> cache_entry;
-      cache_entry.swap(&tmp);
-
-      if (cache_entry->dirty())
-        num_dirty++;
-      else if (CheckEntry(cache_entry.get()))
-        num_entries++;
-      else
-        return ERR_INVALID_ENTRY;
-
-      DCHECK_EQ(i, cache_entry->entry()->Data()->hash & mask_);
-      address.set_value(cache_entry->GetNextAddress());
-      if (!address.is_initialized())
-        break;
-    }
-  }
-
-  Trace("CheckAllEntries End");
-  if (num_entries + num_dirty != data_->header.num_entries) {
-    LOG(ERROR) << "Number of entries " << num_entries << " " << num_dirty <<
-                  " " << data_->header.num_entries;
-    DCHECK_LT(num_entries, data_->header.num_entries);
-    return ERR_NUM_ENTRIES_MISMATCH;
-  }
-
-  return num_dirty;
-}
-
-bool BackendImplV3::CheckEntry(EntryImpl* cache_entry) {
-  bool ok = block_files_.IsValid(cache_entry->entry()->address());
-  ok = ok && block_files_.IsValid(cache_entry->rankings()->address());
-  EntryStore* data = cache_entry->entry()->Data();
-  for (size_t i = 0; i < arraysize(data->data_addr); i++) {
-    if (data->data_addr[i]) {
-      Addr address(data->data_addr[i]);
-      if (address.is_block_file())
-        ok = ok && block_files_.IsValid(address);
-    }
-  }
-
-  return ok && cache_entry->rankings()->VerifyHash();
-}
-
-int BackendImplV3::MaxBuffersSize() {
-  static int64 total_memory = base::SysInfo::AmountOfPhysicalMemory();
-  static bool done = false;
-
-  if (!done) {
-    const int kMaxBuffersSize = 30 * 1024 * 1024;
-
-    // We want to use up to 2% of the computer's memory.
-    total_memory = total_memory * 2 / 100;
-    if (total_memory > kMaxBuffersSize || total_memory <= 0)
-      total_memory = kMaxBuffersSize;
-
-    done = true;
-  }
-
-  return static_cast<int>(total_memory);
-}
-
-#endif  // defined(V3_NOT_JUST_YET_READY).
-
-bool BackendImplV3::IsAllocAllowed(int current_size, int new_size) {
-  return false;
-}
-
-net::CacheType BackendImplV3::GetCacheType() const {
-  return cache_type_;
-}
-
-int32 BackendImplV3::GetEntryCount() const {
-  return 0;
-}
-
-int BackendImplV3::OpenEntry(const std::string& key, Entry** entry,
-                             const CompletionCallback& callback) {
-  return net::ERR_FAILED;
-}
-
-int BackendImplV3::CreateEntry(const std::string& key, Entry** entry,
-                               const CompletionCallback& callback) {
-  return net::ERR_FAILED;
-}
-
-int BackendImplV3::DoomEntry(const std::string& key,
-                             const CompletionCallback& callback) {
-  return net::ERR_FAILED;
-}
-
-int BackendImplV3::DoomAllEntries(const CompletionCallback& callback) {
-  return net::ERR_FAILED;
-}
-
-int BackendImplV3::DoomEntriesBetween(base::Time initial_time,
-                                      base::Time end_time,
-                                      const CompletionCallback& callback) {
-  return net::ERR_FAILED;
-}
-
-int BackendImplV3::DoomEntriesSince(base::Time initial_time,
-                                    const CompletionCallback& callback) {
-  return net::ERR_FAILED;
-}
-
-
-class BackendImplV3::NotImplementedIterator : public Backend::Iterator {
- public:
-  int OpenNextEntry(disk_cache::Entry** next_entry,
-                    const net::CompletionCallback& callback) override {
-    return net::ERR_NOT_IMPLEMENTED;
-  }
-};
-
-scoped_ptr<Backend::Iterator> BackendImplV3::CreateIterator() {
-  return scoped_ptr<Iterator>(new NotImplementedIterator());
-}
-
-void BackendImplV3::GetStats(StatsItems* stats) {
-  NOTIMPLEMENTED();
-}
-
-void BackendImplV3::OnExternalCacheHit(const std::string& key) {
-  NOTIMPLEMENTED();
-}
-
-void BackendImplV3::CleanupCache() {
-}
-
-}  // namespace disk_cache