Remove JsonPrefStore pruning of empty values on write.

Written from https://codereview.chromium.org/12092021

The entire source code was surveyed for existing list/dict prefs for which this change could be problematic, it doesn't look like anything is relying on this internal detail of the API, see this for details: https://docs.google.com/a/chromium.org/spreadsheet/ccc?key=0AtwXJ4IPPZBAdG9rX3RTc3k5Z1pyN3U4b3d4Tkota3c#gid=0

TBR=joth (for minor android_webview side-effects)
BUG=323346

Review URL: https://codereview.chromium.org/81183005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237473 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 0 insertions, 73 deletions

diff --git a/chrome/browser/prefs/chrome_pref_service_unittest.cc b/chrome/browser/prefs/chrome_pref_service_unittest.cc
index 4a453fd4..0d27501 100644
--- a/chrome/browser/prefs/chrome_pref_service_unittest.cc
+++ b/chrome/browser/prefs/chrome_pref_service_unittest.cc
@@ -88,59 +88,6 @@ class ChromePrefServiceUserFilePrefsTest : public testing::Test {
   base::MessageLoop message_loop_;
 };
 
-// Verifies that ListValue and DictionaryValue pref with non emtpy default
-// preserves its empty value.
-TEST_F(ChromePrefServiceUserFilePrefsTest, PreserveEmptyValue) {
-  base::FilePath pref_file = temp_dir_.path().AppendASCII("write.json");
-
-  ASSERT_TRUE(base::CopyFile(
-      data_dir_.AppendASCII("read.need_empty_value.json"),
-      pref_file));
-
-  PrefServiceMockFactory factory;
-  factory.SetUserPrefsFile(pref_file,
-                          message_loop_.message_loop_proxy().get());
-  scoped_refptr<user_prefs::PrefRegistrySyncable> registry(
-      new user_prefs::PrefRegistrySyncable);
-  scoped_ptr<PrefServiceSyncable> prefs(factory.CreateSyncable(registry.get()));
-
-  // Register testing prefs.
-  registry->RegisterListPref("list",
-                             user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
-  registry->RegisterDictionaryPref(
-      "dict",
-      user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
-
-  base::ListValue* non_empty_list = new base::ListValue;
-  non_empty_list->Append(base::Value::CreateStringValue("test"));
-  registry->RegisterListPref("list_needs_empty_value",
-                             non_empty_list,
-                             user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
-
-  base::DictionaryValue* non_empty_dict = new base::DictionaryValue;
-  non_empty_dict->SetString("dummy", "whatever");
-  registry->RegisterDictionaryPref(
-      "dict_needs_empty_value",
-      non_empty_dict,
-      user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
-
-  // Set all testing prefs to empty.
-  ClearListValue(prefs.get(), "list");
-  ClearListValue(prefs.get(), "list_needs_empty_value");
-  ClearDictionaryValue(prefs.get(), "dict");
-  ClearDictionaryValue(prefs.get(), "dict_needs_empty_value");
-
-  // Write to file.
-  prefs->CommitPendingWrite();
-  message_loop_.RunUntilIdle();
-
-  // Compare to expected output.
-  base::FilePath golden_output_file =
-      data_dir_.AppendASCII("write.golden.need_empty_value.json");
-  ASSERT_TRUE(base::PathExists(golden_output_file));
-  EXPECT_TRUE(base::TextContentsEqual(golden_output_file, pref_file));
-}
-
 class ChromePrefServiceWebKitPrefs : public ChromeRenderViewHostTestHarness {
  protected:
   virtual void SetUp() {
diff --git a/chrome/browser/prefs/pref_metrics_service.cc b/chrome/browser/prefs/pref_metrics_service.cc
index 6bbfa4a..7c3f920 100644
--- a/chrome/browser/prefs/pref_metrics_service.cc
+++ b/chrome/browser/prefs/pref_metrics_service.cc
@@ -92,8 +92,6 @@ PrefMetricsService::PrefMetricsService(Profile* profile)
 
   RegisterSyncedPrefObservers();
 
-  MarkNeedsEmptyValueForTrackedPreferences();
-
   // The following code might cause callbacks into this instance before we exit
   // the constructor. This instance should be initialized at this point.
 #if defined(OS_WIN) || defined(OS_MACOSX)
@@ -122,7 +120,6 @@ PrefMetricsService::PrefMetricsService(Profile* profile,
       tracked_pref_path_count_(tracked_pref_path_count),
       checked_tracked_prefs_(false),
       weak_factory_(this) {
-  MarkNeedsEmptyValueForTrackedPreferences();
   CheckTrackedPreferences();
 }
 
@@ -273,19 +270,6 @@ void PrefMetricsService::GetDeviceIdCallback(const std::string& device_id) {
   CheckTrackedPreferences();
 }
 
-void PrefMetricsService::MarkNeedsEmptyValueForTrackedPreferences() {
-  for (int i = 0; i < tracked_pref_path_count_; ++i) {
-    // Skip prefs that haven't been registered.
-    if (!prefs_->FindPreference(tracked_pref_paths_[i]))
-      continue;
-
-    // Make sure tracked prefs are saved to disk even if empty.
-    // TODO(gab): Guarantee this for all prefs at a lower level and remove this
-    // hack.
-    prefs_->MarkUserStoreNeedsEmptyValue(tracked_pref_paths_[i]);
-  }
-}
-
 // To detect changes to Preferences that happen outside of Chrome, we hash
 // selected pref values and save them in local state. CheckTrackedPreferences
 // compares the saved values to the values observed in the profile's prefs. A
diff --git a/chrome/browser/prefs/pref_metrics_service.h b/chrome/browser/prefs/pref_metrics_service.h
index c776b07..d38a006 100644
--- a/chrome/browser/prefs/pref_metrics_service.h
+++ b/chrome/browser/prefs/pref_metrics_service.h
@@ -95,10 +95,6 @@ class PrefMetricsService : public BrowserContextKeyedService {
   // Callback to receive a unique device_id.
   void GetDeviceIdCallback(const std::string& device_id);
 
-  // Marks all tracked preferences as required to save their values even if
-  // empty.
-  void MarkNeedsEmptyValueForTrackedPreferences();
-
   // Checks the tracked preferences against their last known values and reports
   // any discrepancies. This must be called after |device_id| has been set.
   void CheckTrackedPreferences();