Revert of Add SingleLogSource to system_logs sources

chrome/browser/chromeos/system_logs/single_log_source.cc

-// Copyright 2017 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 "chrome/browser/chromeos/system_logs/single_log_source.h"
-
-#include "base/bind.h"
-#include "base/files/file_path.h"
-#include "base/task_scheduler/post_task.h"
-#include "content/public/browser/browser_thread.h"
-
-namespace system_logs {
-
-namespace {
-
-// Converts a logs source type to the corresponding filename. In the future, if
-// non-file source types are added, this function should return an empty string.
-std::string GetLogFileSourceFilename(SingleLogSource::SupportedSource source) {
-  switch (source) {
-    case SingleLogSource::SupportedSource::kMessages:
-      return "/var/log/messages";
-    case SingleLogSource::SupportedSource::kUiLatest:
-      return "/var/log/ui/ui.LATEST";
-  }
-}
-
-}  // namespace
-
-SingleLogSource::SingleLogSource(SupportedSource source)
-    : SystemLogsSource(GetLogFileSourceFilename(source)),
-      num_bytes_read_(0),
-      weak_ptr_factory_(this) {}
-
-SingleLogSource::~SingleLogSource() {}
-
-void SingleLogSource::Fetch(const SysLogsSourceCallback& callback) {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  DCHECK(!callback.is_null());
-
-  SystemLogsResponse* response = new SystemLogsResponse;
-  base::PostTaskWithTraitsAndReply(
-      FROM_HERE,
-      base::TaskTraits(base::MayBlock(), base::TaskPriority::BACKGROUND),
-      base::Bind(&SingleLogSource::ReadFile, weak_ptr_factory_.GetWeakPtr(),
-                 response),
-      base::Bind(callback, base::Owned(response)));
-}
-
-void SingleLogSource::ReadFile(SystemLogsResponse* result) {
-  // Attempt to open the file if it was not previously opened.
-  if (!file_.IsValid()) {
-    file_.Initialize(base::FilePath(source_name()),
-                     base::File::FLAG_OPEN | base::File::FLAG_READ);
-    if (!file_.IsValid())
-      return;
-  }
-
-  // Check for file size reset.
-  const size_t length = file_.GetLength();
-  if (length < num_bytes_read_) {
-    num_bytes_read_ = 0;
-    file_.Seek(base::File::FROM_BEGIN, 0);
-  }
-
-  // Read from file until end.
-  const size_t size_to_read = length - num_bytes_read_;
-  std::string result_string;
-  result_string.resize(size_to_read);
-  const size_t size_read =
-      file_.ReadAtCurrentPos(&result_string[0], size_to_read);
-  result_string.resize(size_read);
-
-  // The reader may only read complete lines.
-  if (result_string.empty() || result_string.back() != '\n') {
-    // If an incomplete line was read, reset the file read offset to before the
-    // most recent read.
-    file_.Seek(base::File::FROM_CURRENT, -size_read);
-    result->emplace(source_name(), "");
-    return;
-  }
-
-  num_bytes_read_ += size_read;
-
-  // Pass it back to the callback.
-  result->emplace(source_name(), anonymizer_.Anonymize(result_string));
-}
-
-}  // namespace system_logs