[Merge to M62] Commit minimal migration status to local state prefs

Commit minimal migration status to local state PrefService.
Introduces a CommitPendingWrite function with a callback to be sure that
prefs landed on disk.

BUG=747907
TBR=pmarko@chromium.org

(cherry picked from commit e1f238f)

Change-Id: I565ffbae7b8a1e934875101012c39c8a9841a139
Reviewed-on: https://chromium-review.googlesource.com/647454
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Commit-Queue: Pavol Marko <pmarko@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#499693}
Reviewed-on: https://chromium-review.googlesource.com/653639
Reviewed-by: Pavol Marko <pmarko@chromium.org>
Cr-Commit-Position: refs/branch-heads/3202@{#52}
Cr-Branched-From: fa6a5d8-refs/heads/master@{#499098}

Author: Pavol Marko

chrome/browser/chromeos/login/existing_user_controller.cc

@@ -1063,15 +1063,19 @@ void ExistingUserController::OnPolicyFetchResult(
     case apu::EcryptfsMigrationAction::kMigrate:
       user_manager::known_user::SetUserHomeMinimalMigrationAttempted(
           user_context.GetAccountId(), false);
-      ShowEncryptionMigrationScreen(user_context,
-                                    EncryptionMigrationMode::START_MIGRATION);
+      user_manager::UserManager::Get()->GetLocalState()->CommitPendingWrite(
+          base::BindOnce(&ExistingUserController::ShowEncryptionMigrationScreen,
+                         weak_factory_.GetWeakPtr(), user_context,
+                         EncryptionMigrationMode::START_MIGRATION));
       break;
 
     case apu::EcryptfsMigrationAction::kAskUser:
       user_manager::known_user::SetUserHomeMinimalMigrationAttempted(
           user_context.GetAccountId(), false);
-      ShowEncryptionMigrationScreen(user_context,
-                                    EncryptionMigrationMode::ASK_USER);
+      user_manager::UserManager::Get()->GetLocalState()->CommitPendingWrite(
+          base::BindOnce(&ExistingUserController::ShowEncryptionMigrationScreen,
+                         weak_factory_.GetWeakPtr(), user_context,
+                         EncryptionMigrationMode::ASK_USER));
       break;
 
     case apu::EcryptfsMigrationAction::kWipe:
@@ -1089,8 +1093,10 @@ void ExistingUserController::OnPolicyFetchResult(
           user_context.GetAccountId());
       user_manager::known_user::SetUserHomeMinimalMigrationAttempted(
           user_context.GetAccountId(), true);
-      ShowEncryptionMigrationScreen(
-          user_context, EncryptionMigrationMode::START_MINIMAL_MIGRATION);
+      user_manager::UserManager::Get()->GetLocalState()->CommitPendingWrite(
+          base::BindOnce(&ExistingUserController::ShowEncryptionMigrationScreen,
+                         weak_factory_.GetWeakPtr(), user_context,
+                         EncryptionMigrationMode::START_MINIMAL_MIGRATION));
       break;
 
     case apu::EcryptfsMigrationAction::kAskForEcryptfsArcUsers:

chrome/browser/prefs/profile_pref_store_manager_unittest.cc

@@ -245,11 +245,8 @@ class ProfilePrefStoreManagerTest : public testing::Test,
       ClearResetRecorded();
       // Force everything to be written to disk, triggering the PrefHashFilter
       // while our RegistryVerifier is watching.
-      pref_store_->CommitPendingWrite();
-      base::RunLoop().RunUntilIdle();
       base::RunLoop run_loop;
-      base::ThreadTaskRunnerHandle::Get()->PostTaskAndReply(
-          FROM_HERE, base::BindOnce(&base::DoNothing), run_loop.QuitClosure());
+      pref_store_->CommitPendingWrite(run_loop.QuitClosure());
       run_loop.Run();
 
       pref_store_->RemoveObserver(&registry_verifier_);
@@ -275,11 +272,8 @@ class ProfilePrefStoreManagerTest : public testing::Test,
                          base::MakeUnique<base::Value>(kFoobar),
                          WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS);
     pref_store->RemoveObserver(&registry_verifier_);
-    pref_store->CommitPendingWrite();
-    base::RunLoop().RunUntilIdle();
     base::RunLoop run_loop;
-    base::ThreadTaskRunnerHandle::Get()->PostTaskAndReply(
-        FROM_HERE, base::BindOnce(&base::DoNothing), run_loop.QuitClosure());
+    pref_store->CommitPendingWrite(run_loop.QuitClosure());
     run_loop.Run();
   }
 

components/prefs/persistent_pref_store.cc

@@ -8,10 +8,6 @@
 
 #include "base/threading/sequenced_task_runner_handle.h"
 
-void PersistentPrefStore::CommitPendingWrite() {
-  CommitPendingWrite(base::OnceClosure());
-}
-
 void PersistentPrefStore::CommitPendingWrite(base::OnceClosure done_callback) {
   // Default behavior for PersistentPrefStore implementation that don't issue
   // disk operations: schedule the callback immediately.

components/prefs/persistent_pref_store.h

@@ -62,9 +62,6 @@ class COMPONENTS_PREFS_EXPORT PersistentPrefStore : public WriteablePrefStore {
   // Owns |error_delegate|.
   virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) = 0;
 
-  // Starts an asynchronous attempt to commit pending writes to disk.
-  void CommitPendingWrite();
-
   // Starts an asynchronous attempt to commit pending writes to disk. Posts a
   // task to run |done_callback| on the current sequence when disk operations,
   // if any, are complete (even if they are unsuccessful).

components/prefs/pref_service.cc

@@ -104,8 +104,12 @@ void PrefService::InitFromStorage(bool async) {
 }
 
 void PrefService::CommitPendingWrite() {
+  CommitPendingWrite(base::OnceClosure());
+}
+
+void PrefService::CommitPendingWrite(base::OnceClosure done_callback) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-  user_pref_store_->CommitPendingWrite();
+  user_pref_store_->CommitPendingWrite(std::move(done_callback));
 }
 
 void PrefService::SchedulePendingLossyWrites() {

components/prefs/pref_service.h

@@ -177,6 +177,11 @@ class COMPONENTS_PREFS_EXPORT PrefService {
   // immediately (basically, during shutdown).
   void CommitPendingWrite();
 
+  // Lands pending writes to disk. This should only be used if we need to save
+  // immediately. |done_callback| will be invoked when changes have been
+  // written.
+  void CommitPendingWrite(base::OnceClosure done_callback);
+
   // Schedule a write if there is any lossy data pending. Unlike
   // CommitPendingWrite() this does not immediately sync to disk, instead it
   // triggers an eventual write if there is lossy data pending and if there