Remove the tracing cache backend.

While working on issue 410276, in particular in
https://codereview.chromium.org/542733002/ , I had to update the
tracing cache backend. Why? Does anyone use it?

Let's remove it instead.

R=pasko@chromium.org,clamy@chromium.org
BUG=None

Review URL: https://codereview.chromium.org/544923002

Cr-Commit-Position: refs/heads/master@{#293505}

net/disk_cache/backend_unittest.cc

@@ -29,7 +29,6 @@
 #include "net/disk_cache/simple/simple_entry_format.h"
 #include "net/disk_cache/simple/simple_test_util.h"
 #include "net/disk_cache/simple/simple_util.h"
-#include "net/disk_cache/tracing/tracing_cache_backend.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #if defined(OS_WIN)
@@ -127,7 +126,6 @@ class DiskCacheBackendTest : public DiskCacheTestWithCache {
   void BackendDisable2();
   void BackendDisable3();
   void BackendDisable4();
-  void TracingBackendBasics();
 };
 
 int DiskCacheBackendTest::GeneratePendingIO(net::TestCompletionCallback* cb) {
@@ -3150,40 +3148,6 @@ TEST_F(DiskCacheBackendTest, ShaderCacheUpdateRankForExternalCacheHit) {
   entry->Close();
 }
 
-void DiskCacheBackendTest::TracingBackendBasics() {
-  InitCache();
-  cache_.reset(new disk_cache::TracingCacheBackend(cache_.Pass()));
-  cache_impl_ = NULL;
-  EXPECT_EQ(net::DISK_CACHE, cache_->GetCacheType());
-  if (!simple_cache_mode_) {
-    EXPECT_EQ(0, cache_->GetEntryCount());
-  }
-
-  net::TestCompletionCallback cb;
-  disk_cache::Entry* entry = NULL;
-  EXPECT_NE(net::OK, OpenEntry("key", &entry));
-  EXPECT_TRUE(NULL == entry);
-
-  ASSERT_EQ(net::OK, CreateEntry("key", &entry));
-  EXPECT_TRUE(NULL != entry);
-
-  disk_cache::Entry* same_entry = NULL;
-  ASSERT_EQ(net::OK, OpenEntry("key", &same_entry));
-  EXPECT_TRUE(NULL != same_entry);
-
-  if (!simple_cache_mode_) {
-    EXPECT_EQ(1, cache_->GetEntryCount());
-  }
-  entry->Close();
-  entry = NULL;
-  same_entry->Close();
-  same_entry = NULL;
-}
-
-TEST_F(DiskCacheBackendTest, TracingBackendBasics) {
-  TracingBackendBasics();
-}
-
 // The Simple Cache backend requires a few guarantees from the filesystem like
 // atomic renaming of recently open files. Those guarantees are not provided in
 // general on Windows.
@@ -3271,13 +3235,6 @@ TEST_F(DiskCacheBackendTest, SimpleCacheAppCacheOnlyDoomAll) {
   BackendDoomAll();
 }
 
-TEST_F(DiskCacheBackendTest, SimpleCacheTracingBackendBasics) {
-  SetSimpleCacheMode();
-  TracingBackendBasics();
-  // TODO(pasko): implement integrity checking on the Simple Backend.
-  DisableIntegrityCheck();
-}
-
 TEST_F(DiskCacheBackendTest, SimpleCacheOpenMissingFile) {
   SetSimpleCacheMode();
   InitCache();

net/disk_cache/cache_creator.cc

@@ -14,10 +14,6 @@
 #include "net/disk_cache/memory/mem_backend_impl.h"
 #include "net/disk_cache/simple/simple_backend_impl.h"
 
-#ifdef USE_TRACING_CACHE_BACKEND
-#include "net/disk_cache/tracing_cache_backend.h"
-#endif
-
 namespace {
 
 // Builds an instance of the backend depending on platform, type, experiments

net/disk_cache/tracing/tracing_cache_backend.h

-// Copyright (c) 2013 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.
-
-#ifndef NET_DISK_CACHE_TRACING_TRACING_CACHE_BACKEND_H_
-#define NET_DISK_CACHE_TRACING_TRACING_CACHE_BACKEND_H_
-
-#include <map>
-
-#include "base/memory/scoped_ptr.h"
-#include "base/memory/weak_ptr.h"
-#include "net/disk_cache/blockfile/stats.h"
-#include "net/disk_cache/disk_cache.h"
-
-namespace disk_cache {
-
-class EntryProxy;
-
-// The TracingCacheBackend implements the Cache Backend interface. It intercepts
-// all backend operations from the IO thread and records the time from the start
-// of the operation until the result is delivered.
-class NET_EXPORT TracingCacheBackend : public Backend,
-    public base::SupportsWeakPtr<TracingCacheBackend> {
- public:
-  explicit TracingCacheBackend(scoped_ptr<Backend> backend);
-
-  virtual net::CacheType GetCacheType() const OVERRIDE;
-  virtual int32 GetEntryCount() const OVERRIDE;
-  virtual int OpenEntry(const std::string& key, Entry** entry,
-                        const CompletionCallback& callback) OVERRIDE;
-  virtual int CreateEntry(const std::string& key, Entry** entry,
-                          const CompletionCallback& callback) OVERRIDE;
-  virtual int DoomEntry(const std::string& key,
-                        const CompletionCallback& callback) OVERRIDE;
-  virtual int DoomAllEntries(const CompletionCallback& callback) OVERRIDE;
-  virtual int DoomEntriesBetween(base::Time initial_time,
-                                 base::Time end_time,
-                                 const CompletionCallback& callback) OVERRIDE;
-  virtual int DoomEntriesSince(base::Time initial_time,
-                               const CompletionCallback& callback) OVERRIDE;
-  virtual int OpenNextEntry(void** iter, Entry** next_entry,
-                            const CompletionCallback& callback) OVERRIDE;
-  virtual void EndEnumeration(void** iter) OVERRIDE;
-  virtual void GetStats(StatsItems* stats) OVERRIDE;
-  virtual void OnExternalCacheHit(const std::string& key) OVERRIDE;
-
- private:
-  friend class EntryProxy;
-  enum Operation {
-    OP_OPEN,
-    OP_CREATE,
-    OP_DOOM_ENTRY,
-    OP_READ,
-    OP_WRITE
-  };
-
-  virtual ~TracingCacheBackend();
-
-  EntryProxy* FindOrCreateEntryProxy(Entry* entry);
-
-  void OnDeleteEntry(Entry* e);
-
-  void RecordEvent(base::TimeTicks start_time, Operation op, std::string key,
-                   Entry* entry, int result);
-
-  void BackendOpComplete(base::TimeTicks start_time, Operation op,
-                         std::string key, Entry** entry,
-                         const CompletionCallback& callback, int result);
-
-  net::CompletionCallback BindCompletion(Operation op,
-                                         base::TimeTicks start_time,
-                                         const std::string& key, Entry **entry,
-                                         const net::CompletionCallback& cb);
-
-  scoped_ptr<Backend> backend_;
-  typedef std::map<Entry*, EntryProxy*> EntryToProxyMap;
-  EntryToProxyMap open_entries_;
-
-  DISALLOW_COPY_AND_ASSIGN(TracingCacheBackend);
-};
-
-}  // namespace disk_cache
-
-#endif  // NET_DISK_CACHE_TRACING_TRACING_CACHE_BACKEND_H_

net/net.gyp

@@ -7,7 +7,6 @@
     'chromium_code': 1,
 
     'linux_link_kerberos%': 0,
-    'use_tracing_cache_backend%': 0,
     'conditions': [
       ['chromeos==1 or embedded==1 or OS=="android" or OS=="ios"', {
         # Disable Kerberos on ChromeOS, Android and iOS, at least for now.
@@ -203,11 +202,6 @@
             'dns/dns_client.cc',
           ],
         }],
-        ['use_tracing_cache_backend==1', {
-          'defines': [
-            'USE_TRACING_CACHE_BACKEND'
-          ],
-         }],
         ['use_openssl==1', {
             'sources!': [
               'base/crypto_module_nss.cc',

net/net.gypi

@@ -474,8 +474,6 @@
       'disk_cache/simple/simple_util.h',
       'disk_cache/simple/simple_version_upgrade.cc',
       'disk_cache/simple/simple_version_upgrade.h',
-      'disk_cache/tracing/tracing_cache_backend.cc',
-      'disk_cache/tracing/tracing_cache_backend.h',
       'dns/address_sorter.h',
       'dns/address_sorter_posix.cc',
       'dns/address_sorter_posix.h',