Update from https://crrev.com/329939

base/prefs/pref_service.cc

Index: base/prefs/pref_service.cc
diff --git a/base/prefs/pref_service.cc b/base/prefs/pref_service.cc
index 3ccdae75a961c99611268affc40265dd6a4643ca..6e1d58ca0f163eff22c4048e6691ba3192bec884 100644
--- a/base/prefs/pref_service.cc
+++ b/base/prefs/pref_service.cc
@@ -38,6 +38,19 @@ class ReadErrorHandler : public PersistentPrefStore::ReadErrorDelegate {
   base::Callback<void(PersistentPrefStore::PrefReadError)> callback_;
 };
 
+// Returns the WriteablePrefStore::PrefWriteFlags for the pref with the given
+// |path|.
+uint32 GetWriteFlags(const PrefService::Preference* pref) {
+  uint32 write_flags = WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS;
+
+  if (!pref)
+    return write_flags;
+
+  if (pref->registration_flags() & PrefRegistry::LOSSY_PREF)
+    write_flags |= WriteablePrefStore::LOSSY_PREF_WRITE_FLAG;
+  return write_flags;
+}
+
 }  // namespace
 
 PrefService::PrefService(
@@ -177,8 +190,7 @@ scoped_ptr<base::DictionaryValue> PrefService::GetPreferenceValues() const {
   DCHECK(CalledOnValidThread());
   scoped_ptr<base::DictionaryValue> out(new base::DictionaryValue);
   for (const auto& it : *pref_registry_) {
-    const base::Value* value = GetPreferenceValue(it.first);
-    out->Set(it.first, value->DeepCopy());
+    out->Set(it.first, GetPreferenceValue(it.first)->CreateDeepCopy());
   }
   return out.Pass();
 }
@@ -191,7 +203,7 @@ scoped_ptr<base::DictionaryValue> PrefService::GetPreferenceValuesOmitDefaults()
     const Preference* pref = FindPreference(it.first);
     if (pref->IsDefaultValue())
       continue;
-    out->Set(it.first, pref->GetValue()->DeepCopy());
+    out->Set(it.first, pref->GetValue()->CreateDeepCopy());
   }
   return out.Pass();
 }
@@ -203,7 +215,7 @@ PrefService::GetPreferenceValuesWithoutPathExpansion() const {
   for (const auto& it : *pref_registry_) {
     const base::Value* value = GetPreferenceValue(it.first);
     DCHECK(value);
-    out->SetWithoutPathExpansion(it.first, value->DeepCopy());
+    out->SetWithoutPathExpansion(it.first, value->CreateDeepCopy());
   }
   return out.Pass();
 }
@@ -357,7 +369,7 @@ void PrefService::ClearPref(const std::string& path) {
     NOTREACHED() << "Trying to clear an unregistered pref: " << path;
     return;
   }
-  user_pref_store_->RemoveValue(path);
+  user_pref_store_->RemoveValue(path, GetWriteFlags(pref));
 }
 
 void PrefService::Set(const std::string& path, const base::Value& value) {
@@ -454,14 +466,14 @@ base::Value* PrefService::GetMutableUserPref(const std::string& path,
     } else {
       NOTREACHED();
     }
-    user_pref_store_->SetValueSilently(path, value);
+    user_pref_store_->SetValueSilently(path, value, GetWriteFlags(pref));
   }
   return value;
 }
 
 void PrefService::ReportUserPrefChanged(const std::string& key) {
   DCHECK(CalledOnValidThread());
-  user_pref_store_->ReportValueChanged(key);
+  user_pref_store_->ReportValueChanged(key, GetWriteFlags(FindPreference(key)));
 }
 
 void PrefService::SetUserPrefValue(const std::string& path,
@@ -481,7 +493,7 @@ void PrefService::SetUserPrefValue(const std::string& path,
     return;
   }
 
-  user_pref_store_->SetValue(path, owned_value.release());
+  user_pref_store_->SetValue(path, owned_value.release(), GetWriteFlags(pref));
 }
 
 void PrefService::UpdateCommandLinePrefStore(PrefStore* command_line_store) {
@@ -496,6 +508,9 @@ PrefService::Preference::Preference(const PrefService* service,
                                     base::Value::Type type)
     : name_(name), type_(type), pref_service_(service) {
   DCHECK(service);
+  // Cache the registration flags at creation time to avoid multiple map lookups
+  // later.
+  registration_flags_ = service->pref_registry_->GetRegistrationFlags(name_);
 }
 
 const std::string PrefService::Preference::name() const {