Remove all code related to the PreRead field trial.

chrome/browser/chrome_browser_main.cc

 // 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 "chrome/browser/chrome_browser_main.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 12 matching lines @@
 #include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/path_service.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/run_loop.h"
+#include "base/strings/string16.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/sys_info.h"
 #include "base/task_scheduler/scheduler_worker_pool_params.h"
 #include "base/task_scheduler/switches.h"
 #include "base/task_scheduler/task_scheduler.h"
 #include "base/task_scheduler/task_traits.h"
@@ skipping 148 matching lines @@
 #include "chromeos/settings/cros_settings_names.h"
 #endif  // defined(OS_CHROMEOS)
 
 // TODO(port): several win-only methods have been pulled out of this, but
 // BrowserMain() as a whole needs to be broken apart so that it's usable by
 // other platforms. For now, it's just a stub. This is a serious work in
 // progress and should not be taken as an indication of a real refactoring.
 
 #if defined(OS_WIN)
 #include "base/trace_event/trace_event_etw_export_win.h"
+#include "base/win/registry.h"
 #include "base/win/win_util.h"
 #include "base/win/windows_version.h"
 #include "chrome/browser/chrome_browser_main_win.h"
 #include "chrome/browser/component_updater/sw_reporter_installer_win.h"
 #include "chrome/browser/downgrade/user_data_downgrade.h"
 #include "chrome/browser/first_run/try_chrome_dialog_view.h"
 #include "chrome/browser/first_run/upgrade_util_win.h"
-#include "chrome/browser/metrics/chrome_metrics_service_accessor.h"
 #include "chrome/browser/ui/network_profile_bubble.h"
 #include "chrome/browser/win/browser_util.h"
 #include "chrome/browser/win/chrome_select_file_dialog_factory.h"
 #include "chrome/installer/util/browser_distribution.h"
 #include "chrome/installer/util/helper.h"
 #include "chrome/installer/util/install_util.h"
 #include "chrome/installer/util/shell_util.h"
-#include "components/startup_metric_utils/common/pre_read_field_trial_utils_win.h"
 #include "ui/base/l10n/l10n_util_win.h"
 #include "ui/shell_dialogs/select_file_dialog.h"
 #endif  // defined(OS_WIN)
 
 #if defined(OS_MACOSX)
 #include <Security/Security.h>
 
 #include "base/mac/scoped_nsautorelease_pool.h"
 #include "chrome/browser/mac/keystone_glue.h"
 #endif  // defined(OS_MACOSX)
@@ skipping 503 matching lines @@
   ~ScopedMainMessageLoopRunEvent() {
     TRACE_EVENT_ASYNC_END0("toplevel",
                            "ChromeBrowserMainParts::MainMessageLoopRun", this);
   }
 };
 
 }  // namespace
 
 namespace chrome_browser {
 
-#if defined(OS_WIN)
-// Helper function to setup the pre-read field trial. This function is defined
-// outside of the anonymous namespace to allow it to be friend with
-// ChromeMetricsServiceAccessor.
-void SetupPreReadFieldTrial() {
-  const base::string16 registry_path =
-      BrowserDistribution::GetDistribution()->GetRegistryPath();
-
-  // Register a synthetic field trial with the PreRead group used during the
-  // current startup. This must be done before the first metric log
-  // (metrics::MetricLog) is created. Otherwise, UMA metrics generated during
-  // startup won't be correctly annotated. The current function is always called
-  // before the first metric log is created, as part of
-  // ChromeBrowserMainParts::PreMainMessageLoopRun().
-  startup_metric_utils::RegisterPreReadSyntheticFieldTrial(
-      registry_path,
-      base::Bind(&ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial));
-
-  // Initialize the PreRead options for the current process.
-  startup_metric_utils::InitializePreReadOptions(registry_path);
-
-  // After startup is complete, update the PreRead group in the registry. The
-  // group written in the registry will be used for the next startup.
-  BrowserThread::PostAfterStartupTask(
-      FROM_HERE, content::BrowserThread::GetBlockingPool(),
-      base::Bind(&startup_metric_utils::UpdatePreReadOptions, registry_path));
-}
-#endif  // defined(OS_WIN)
-
 // This error message is not localized because we failed to load the
 // localization data files.
 #if defined(OS_WIN)
 const char kMissingLocaleDataTitle[] = "Missing File Error";
 #endif  // defined(OS_WIN)
 
 #if defined(OS_WIN)
 // TODO(port) This should be used on Linux Aura as well. http://crbug.com/338969
 const char kMissingLocaleDataMessage[] =
     "Unable to find locale data files. Please reinstall.";
@@ skipping 165 matching lines @@
   // Register a synthetic field trial for the sampling profiler configuration
   // that was already chosen.
   sampling_profiler_config_.RegisterSyntheticFieldTrial();
 
 #if defined(OS_WIN) || defined(OS_MACOSX) || \
     (defined(OS_LINUX) && !defined(OS_CHROMEOS))
   metrics::DesktopEngagementService::Initialize();
 #endif
 
 #if defined(OS_WIN)
-  chrome_browser::SetupPreReadFieldTrial();
+  // Cleanup the PreRead field trial registry key.
+  // TODO(fdoray): Remove this when M56 hits stable.
+  const base::string16 pre_read_field_trial_registry_path =
+      BrowserDistribution::GetDistribution()->GetRegistryPath() +
+      L"\\PreReadFieldTrial";
+  base::win::RegKey(HKEY_CURRENT_USER,
+                    pre_read_field_trial_registry_path.c_str(), KEY_SET_VALUE)
+      .DeleteKey(L"");
 #endif  // defined(OS_WIN)
 }
 
 // ChromeBrowserMainParts: |SetupMetricsAndFieldTrials()| related --------------
 
 void ChromeBrowserMainParts::StartMetricsRecording() {
   TRACE_EVENT0("startup", "ChromeBrowserMainParts::StartMetricsRecording");
 
   g_browser_process->metrics_service()->CheckForClonedInstall(
       BrowserThread::GetTaskRunnerForThread(BrowserThread::FILE));
@@ skipping 1249 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif  // defined(OS_CHROMEOS)
 #endif  // defined(OS_ANDROID)
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }