Add histograms to track synced pref changes.

chrome/browser/prefs/pref_metrics_service.cc

Index: chrome/browser/prefs/pref_metrics_service.cc
diff --git a/chrome/browser/prefs/pref_metrics_service.cc b/chrome/browser/prefs/pref_metrics_service.cc
index bcac81817db093c1ce75ec64fce142892c0ac309..467eee3472582b28b137c66438ffcfabf55544b6 100644
--- a/chrome/browser/prefs/pref_metrics_service.cc
+++ b/chrome/browser/prefs/pref_metrics_service.cc
@@ -4,17 +4,40 @@
 
 #include "chrome/browser/prefs/pref_metrics_service.h"
 
+#include "base/bind.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/pref_service.h"
+#include "chrome/browser/prefs/pref_service_syncable.h"
 #include "chrome/browser/prefs/session_startup_pref.h"
+#include "chrome/browser/prefs/synced_pref_change_registrar.h"
 #include "chrome/browser/profiles/incognito_helpers.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/pref_names.h"
 #include "components/browser_context_keyed_service/browser_context_dependency_manager.h"
+#include "net/base/registry_controlled_domains/registry_controlled_domain.h"
+
+namespace {
+
+// Converts a host name into a domain name for easier matching.
+std::string GetDomainFromHost(const std::string& host) {
+  return net::registry_controlled_domains::GetDomainAndRegistry(
+      host,
+      net::registry_controlled_domains::EXCLUDE_PRIVATE_REGISTRIES);
+}
+
+}  // namespace
+
+// Declare storage for this value so it can be used as an argument to Bind.
+const int SessionStartupPref::kPrefValueMax;
 
 PrefMetricsService::PrefMetricsService(Profile* profile)
     : profile_(profile) {
   RecordLaunchPrefs();
+
+  PrefServiceSyncable* prefs = PrefServiceSyncable::FromProfile(profile_);
+  synced_pref_change_registrar_.reset(new SyncedPrefChangeRegistrar(prefs));
+
+  RegisterSyncedPrefObservers();
 }
 
 PrefMetricsService::~PrefMetricsService() {
@@ -40,6 +63,76 @@ void PrefMetricsService::RecordLaunchPrefs() {
   }
 }
 
+void PrefMetricsService::RegisterSyncedPrefObservers() {
+  LogHistogramValueCallback booleanHandler = base::Bind(
+      &PrefMetricsService::LogBooleanPrefChange, base::Unretained(this));
+
+  AddPrefObserver(prefs::kShowHomeButton, "ShowHomeButton", booleanHandler);
+  AddPrefObserver(prefs::kHomePageIsNewTabPage, "HomePageIsNewTabPage",
+                  booleanHandler);
+
+  AddPrefObserver(prefs::kRestoreOnStartup, "StartupPageLoadSettings",
+                  base::Bind(&PrefMetricsService::LogIntegerPrefChange,
+                             base::Unretained(this),
+                             SessionStartupPref::kPrefValueMax));
+}
+
+void PrefMetricsService::AddPrefObserver(
+    const std::string& path,
+    const std::string& histogram_name_prefix,
+    const LogHistogramValueCallback& callback) {
+  synced_pref_change_registrar_->Add(path.c_str(),
+      base::Bind(&PrefMetricsService::OnPrefChanged,
+                 base::Unretained(this),
+                 histogram_name_prefix, callback));
+}
+
+void PrefMetricsService::OnPrefChanged(
+    const std::string& histogram_name_prefix,
+    const LogHistogramValueCallback& callback,
+    const std::string& path,
+    bool from_sync) {
+  PrefServiceSyncable* prefs = PrefServiceSyncable::FromProfile(profile_);
+  const PrefService::Preference* pref = prefs->FindPreference(path.c_str());
+  DCHECK(pref);
+  std::string source_name(
+      from_sync ? ".PulledFromSync" : ".PushedToSync");
+  std::string histogram_name("Settings." + histogram_name_prefix + source_name);
+  callback.Run(histogram_name, pref->GetValue());
+};
+
+void PrefMetricsService::LogBooleanPrefChange(const std::string& histogram_name,
+                                              const Value* value) {
+  bool boolean_value = false;
+  if (!value->GetAsBoolean(&boolean_value))
+    return;
+  UMA_HISTOGRAM_BOOLEAN(histogram_name.c_str(), boolean_value);
+}
+
+void PrefMetricsService::LogIntegerPrefChange(int boundary_value,
+                                              const std::string& histogram_name,
+                                              const Value* value) {
+  int integer_value = 0;
+  if (!value->GetAsInteger(&integer_value))
+    return;
+  UMA_HISTOGRAM_ENUMERATION(histogram_name.c_str(), integer_value,
+                            boundary_value);
+}
+
+void PrefMetricsService::LogListPrefChange(
+    const LogHistogramValueCallback& item_callback,
+    const std::string& histogram_name,
+    const Value* value) {
+  const ListValue* items = NULL;
+  if (!value->GetAsList(&items))
+    return;
+  for (size_t i = 0; i < items->GetSize(); ++i) {
+    const Value *item_value = NULL;
+    if (items->Get(i, &item_value))
+      item_callback.Run(histogram_name, item_value);
+  }
+}
+
 // static
 PrefMetricsService::Factory* PrefMetricsService::Factory::GetInstance() {
   return Singleton<PrefMetricsService::Factory>::get();