[Sync:USS] Add NigoriStorage::ClearData()

We need to remove all stored sync metadata when user disabled sync.
Nigori is not user type, so we have to remove everything related in
this case. NigoriStorage::ClearData() just removes the corresponding
file.

Bug: 922900
Change-Id: Icfbb27f4a693122b3d048bdba857764d5dd83a97
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1782848
Commit-Queue: Maksim Moskvitin <mmoskvitin@google.com>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693149}

components/sync/nigori/nigori_storage.h

@@ -24,6 +24,9 @@ class NigoriStorage {
   // was stored, returns base::nullopt.
   virtual base::Optional<sync_pb::NigoriLocalData> RestoreData() = 0;
 
+  // Removes all previously stored data.
+  virtual void ClearData() = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(NigoriStorage);
 };

components/sync/nigori/nigori_storage_impl.cc

@@ -68,4 +68,8 @@ base::Optional<sync_pb::NigoriLocalData> NigoriStorageImpl::RestoreData() {
   return data;
 }
 
+void NigoriStorageImpl::ClearData() {
+  base::DeleteFile(path_, /*recursive=*/false);
+}
+
 }  // namespace syncer

components/sync/nigori/nigori_storage_impl.h

@@ -23,6 +23,7 @@ class NigoriStorageImpl : public NigoriStorage {
   // Encrypts |data| and atomically stores it in binary file.
   void StoreData(const sync_pb::NigoriLocalData& data) override;
   base::Optional<sync_pb::NigoriLocalData> RestoreData() override;
+  void ClearData() override;
 
  private:
   base::FilePath path_;

components/sync/nigori/nigori_storage_impl_unittest.cc

@@ -4,6 +4,7 @@
 
 #include "components/sync/nigori/nigori_storage_impl.h"
 
+#include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "components/sync/base/fake_encryptor.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -58,6 +59,15 @@ TEST_F(NigoriStorageImplTest, ShouldReturnNulloptWhenFileNotExists) {
   EXPECT_EQ(storage.RestoreData(), base::nullopt);
 }
 
+TEST_F(NigoriStorageImplTest, ShouldRemoveFile) {
+  NigoriStorageImpl storage(GetFilePath(), encryptor());
+  sync_pb::NigoriLocalData data = MakeSomeNigoriLocalData();
+  storage.StoreData(data);
+  ASSERT_TRUE(base::PathExists(GetFilePath()));
+  storage.ClearData();
+  EXPECT_FALSE(base::PathExists(GetFilePath()));
+}
+
 }  // namespace
 
 }  // namespace syncer

components/sync/nigori/nigori_sync_bridge_impl_unittest.cc

@@ -272,6 +272,7 @@ class MockNigoriStorage : public NigoriStorage {
 
   MOCK_METHOD1(StoreData, void(const sync_pb::NigoriLocalData&));
   MOCK_METHOD0(RestoreData, base::Optional<sync_pb::NigoriLocalData>());
+  MOCK_METHOD0(ClearData, void());
 };
 
 class NigoriSyncBridgeImplTest : public testing::Test {