Split file_observers.h into three files for each class

content/public/test/test_file_system_backend.cc

 // Copyright 2013 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 "content/public/test/test_file_system_backend.h"
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/file_util.h"
 #include "base/sequenced_task_runner.h"
 #include "webkit/browser/blob/file_stream_reader.h"
 #include "webkit/browser/fileapi/copy_or_move_file_validator.h"
-#include "webkit/browser/fileapi/file_observers.h"
+#include "webkit/browser/fileapi/file_access_observer.h"
+#include "webkit/browser/fileapi/file_change_observer.h"
 #include "webkit/browser/fileapi/file_system_operation.h"
 #include "webkit/browser/fileapi/file_system_operation_context.h"
 #include "webkit/browser/fileapi/file_system_quota_util.h"
+#include "webkit/browser/fileapi/file_update_observer.h"
 #include "webkit/browser/fileapi/local_file_util.h"
 #include "webkit/browser/fileapi/native_file_util.h"
 #include "webkit/browser/fileapi/sandbox_file_stream_writer.h"
 #include "webkit/browser/quota/quota_manager.h"
 #include "webkit/common/fileapi/file_system_util.h"
 
 namespace fileapi {
 
 namespace {
 
@@ skipping 209 matching lines @@
   return quota_util_->GetUpdateObservers(type);
 }
 
 void TestFileSystemBackend::AddFileChangeObserver(
     FileChangeObserver* observer) {
   quota_util_->AddFileChangeObserver(
       kFileSystemTypeTest, observer, quota_util_->task_runner());
 }
 
 }  // namespace fileapi