Refactor out a new class for syncing field trials in child processes.

chrome/renderer/chrome_render_thread_observer.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/renderer/chrome_render_thread_observer.h"
 
 #include <stddef.h>
 
 #include <limits>
 #include <memory>
 #include <set>
 #include <utility>
 #include <vector>
 
-#include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/files/file_util.h"
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/path_service.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "chrome/common/child_process_logging.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/media/media_resource_provider.h"
 #include "chrome/common/net/net_resource_provider.h"
 #include "chrome/common/render_messages.h"
 #include "chrome/common/resource_usage_reporter.mojom.h"
 #include "chrome/common/resource_usage_reporter_type_converters.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/renderer/content_settings_observer.h"
 #include "chrome/renderer/security_filter_peer.h"
-#include "components/variations/variations_util.h"
 #include "content/public/child/resource_dispatcher_delegate.h"
 #include "content/public/common/service_registry.h"
 #include "content/public/renderer/render_thread.h"
 #include "content/public/renderer/render_view.h"
 #include "content/public/renderer/render_view_visitor.h"
 #include "media/base/media_resources.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "net/base/net_errors.h"
 #include "net/base/net_module.h"
 #include "third_party/WebKit/public/web/WebCache.h"
@@ skipping 179 matching lines @@
     base::WeakPtr<ChromeRenderThreadObserver> observer,
     mojo::InterfaceRequest<mojom::ResourceUsageReporter> request) {
   new ResourceUsageReporterImpl(observer, std::move(request));
 }
 
 }  // namespace
 
 bool ChromeRenderThreadObserver::is_incognito_process_ = false;
 
 ChromeRenderThreadObserver::ChromeRenderThreadObserver()
-    : weak_factory_(this) {
+    : field_trial_syncer_(content::RenderThread::Get()), weak_factory_(this) {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
 
   RenderThread* thread = RenderThread::Get();
   resource_delegate_.reset(new RendererResourceDelegate());
   thread->SetResourceDispatcherDelegate(resource_delegate_.get());
 
   thread->GetServiceRegistry()->AddService(
       base::Bind(CreateResourceUsageReporter, weak_factory_.GetWeakPtr()));
 
   // Configure modules that need access to resources.
   net::NetModule::SetResourceProvider(chrome_common_net::NetResourceProvider);
   media::SetLocalizedStringProvider(
       chrome_common_media::LocalizedStringProvider);
 
-  InitFieldTrialObserving(command_line);
+  field_trial_syncer_.InitFieldTrialObserving(command_line);
 
   // chrome-native: is a scheme used for placeholder navigations that allow
   // UIs to be drawn with platform native widgets instead of HTML.  These pages
   // should not be accessible, and should also be treated as empty documents
   // that can commit synchronously.  No code should be runnable in these pages,
   // so it should not need to access anything nor should it allow javascript
   // URLs since it should never be visible to the user.
   WebString native_scheme(base::ASCIIToUTF16(chrome::kChromeNativeScheme));
   WebSecurityPolicy::registerURLSchemeAsDisplayIsolated(native_scheme);
   WebSecurityPolicy::registerURLSchemeAsEmptyDocument(native_scheme);
   WebSecurityPolicy::registerURLSchemeAsNoAccess(native_scheme);
   WebSecurityPolicy::registerURLSchemeAsNotAllowingJavascriptURLs(
       native_scheme);
 }
 
 ChromeRenderThreadObserver::~ChromeRenderThreadObserver() {}
 
-void ChromeRenderThreadObserver::InitFieldTrialObserving(
-    const base::CommandLine& command_line) {
-  // Set up initial set of crash dump data for field trials in this renderer.
-  variations::SetVariationListCrashKeys();
-
-  // Listen for field trial activations to report them to the browser.
-  base::FieldTrialList::AddObserver(this);
-
-  // Some field trials may have been activated before this point. Notify the
-  // browser of these activations now. To detect these, take the set difference
-  // of currently active trials with the initially active trials.
-  base::FieldTrial::ActiveGroups initially_active_trials;
-  base::FieldTrialList::GetActiveFieldTrialGroupsFromString(
-      command_line.GetSwitchValueASCII(switches::kForceFieldTrials),
-      &initially_active_trials);
-  std::set<std::string> initially_active_trials_set;
-  for (const auto& entry : initially_active_trials) {
-    initially_active_trials_set.insert(std::move(entry.trial_name));
-  }
-
-  base::FieldTrial::ActiveGroups current_active_trials;
-  base::FieldTrialList::GetActiveFieldTrialGroups(&current_active_trials);
-  for (const auto& trial : current_active_trials) {
-    if (!ContainsKey(initially_active_trials_set, trial.trial_name))
-      OnFieldTrialGroupFinalized(trial.trial_name, trial.group_name);
-  }
-}
-
 bool ChromeRenderThreadObserver::OnControlMessageReceived(
     const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(ChromeRenderThreadObserver, message)
     IPC_MESSAGE_HANDLER(ChromeViewMsg_SetIsIncognitoProcess,
                         OnSetIsIncognitoProcess)
     IPC_MESSAGE_HANDLER(ChromeViewMsg_SetFieldTrialGroup, OnSetFieldTrialGroup)
     IPC_MESSAGE_HANDLER(ChromeViewMsg_SetContentSettingRules,
                         OnSetContentSettingRules)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
 }
 
 void ChromeRenderThreadObserver::OnSetIsIncognitoProcess(
     bool is_incognito_process) {
   is_incognito_process_ = is_incognito_process;
 }
 
 void ChromeRenderThreadObserver::OnSetContentSettingRules(
     const RendererContentSettingRules& rules) {
   content_setting_rules_ = rules;
 }
 
 void ChromeRenderThreadObserver::OnSetFieldTrialGroup(
-    const std::string& field_trial_name,
+    const std::string& trial_name,
     const std::string& group_name) {
-  base::FieldTrial* trial =
-      base::FieldTrialList::CreateFieldTrial(field_trial_name, group_name);
-  // Ensure the trial is marked as "used" by calling group() on it if it is
-  // marked as activated.
-  trial->group();
-  variations::SetVariationListCrashKeys();
+  field_trial_syncer_.OnSetFieldTrialGroup(trial_name, group_name);
 }
 
 const RendererContentSettingRules*
 ChromeRenderThreadObserver::content_setting_rules() const {
   return &content_setting_rules_;
 }
-
-void ChromeRenderThreadObserver::OnFieldTrialGroupFinalized(
-    const std::string& trial_name,
-    const std::string& group_name) {
-  content::RenderThread::Get()->Send(
-      new ChromeViewHostMsg_FieldTrialActivated(trial_name));
-}