Allow ImportantFileWriter to take in a pre-write callback.

base/files/important_file_writer.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/files/important_file_writer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <string>
@@ skipping 39 matching lines @@
 
 void LogFailure(const FilePath& path, TempFileFailure failure_code,
                 StringPiece message) {
   UMA_HISTOGRAM_ENUMERATION("ImportantFile.TempFileFailures", failure_code,
                             TEMP_FILE_FAILURE_MAX);
   DPLOG(WARNING) << "temp file failure: " << path.value() << " : " << message;
 }
 
 // Helper function to call WriteFileAtomically() with a
 // std::unique_ptr<std::string>.
-void WriteScopedStringToFileAtomically(const FilePath& path,
-                                       std::unique_ptr<std::string> data,
-                                       Callback<void(bool success)> callback) {
+void WriteScopedStringToFileAtomically(
+    const FilePath& path,
+    std::unique_ptr<std::string> data,
+    Closure before_write_callback,
+    Callback<void(bool success)> after_write_callback) {
+  if (!before_write_callback.is_null())
+    before_write_callback.Run();
+
   bool result = ImportantFileWriter::WriteFileAtomically(path, *data);
 
-  if (!callback.is_null())
-    callback.Run(result);
+  if (!after_write_callback.is_null())
+    after_write_callback.Run(result);
 }
 
 }  // namespace
 
 // static
 bool ImportantFileWriter::WriteFileAtomically(const FilePath& path,
                                               StringPiece data) {
 #if defined(OS_CHROMEOS)
   // On Chrome OS, chrome gets killed when it cannot finish shutdown quickly,
   // and this function seems to be one of the slowest shutdown steps.
@@ skipping 89 matching lines @@
   DCHECK(CalledOnValidThread());
   if (!IsValueInRangeForNumericType<int32_t>(data->length())) {
     NOTREACHED();
     return;
   }
 
   if (HasPendingWrite())
     timer_.Stop();
 
   Closure task = Bind(&WriteScopedStringToFileAtomically, path_, Passed(&data),
-                      Passed(&on_next_write_callback_));
+                      Passed(&before_next_write_callback_),
+                      Passed(&after_next_write_callback_));
 
   if (!task_runner_->PostTask(FROM_HERE, MakeCriticalClosure(task))) {
     // Posting the task to background message loop is not expected
     // to fail, but if it does, avoid losing data and just hit the disk
     // on the current thread.
     NOTREACHED();
 
     task.Run();
   }
 }
@@ skipping 15 matching lines @@
   std::unique_ptr<std::string> data(new std::string);
   if (serializer_->SerializeData(data.get())) {
     WriteNow(std::move(data));
   } else {
     DLOG(WARNING) << "failed to serialize data to be saved in "
                   << path_.value();
   }
   serializer_ = nullptr;
 }
 
-void ImportantFileWriter::RegisterOnNextWriteCallback(
-    const Callback<void(bool success)>& on_next_write_callback) {
-  on_next_write_callback_ = on_next_write_callback;
+void ImportantFileWriter::RegisterOnNextWriteCallbacks(
+    const Closure& before_next_write_callback,
+    const Callback<void(bool success)>& after_next_write_callback) {
+  before_next_write_callback_ = before_next_write_callback;
+  after_next_write_callback_ = after_next_write_callback;
 }
 
 }  // namespace base