Add SingleLogSource to system_logs sources

chrome/browser/chromeos/system_logs/single_log_source.h

+// 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_SYSTEM_LOGS_SINGLE_LOG_SOURCE_H_
+#define CHROME_BROWSER_CHROMEOS_SYSTEM_LOGS_SINGLE_LOG_SOURCE_H_
+
+#include <stddef.h>
+
+#include "base/files/file.h"
+#include "base/macros.h"
+#include "chrome/browser/feedback/system_logs/system_logs_fetcher_base.h"
+#include "components/feedback/anonymizer_tool.h"
+
+namespace system_logs {
+
+// Gathers log data from a single source, possibly incrementally.
+class SingleLogSource : public SystemLogsSource {
+ public:
+  enum class SupportedSource {
+    // For /var/log/messages.
+    kMessages,
+
+    // For /var/log/ui/ui.LATEST.
+    kUiLatest,
+  };
+
+  explicit SingleLogSource(SupportedSource source);
+  ~SingleLogSource() override;
+
+  // system_logs::SystemLogsSource:
+  void Fetch(const SysLogsSourceCallback& callback) override;
+
+ protected:
+  // For unit testing.
+  base::File* mutable_file() { return &file_; }
+
+ private:
+  // Reads all available content from |file_| that has not already been read.
+  void ReadFile(SystemLogsResponse* result);
+
+  // Keeps track of how much data has been read from |file_|.
+  size_t num_bytes_read_;
+
+  // Handle for reading the log file that is source of logging data.
+  base::File file_;
+
+  // For removing PII from log results.
+  feedback::AnonymizerTool anonymizer_;
+
+  DISALLOW_COPY_AND_ASSIGN(SingleLogSource);
+};
+
+}  // namespace system_logs
+
+#endif  // CHROME_BROWSER_CHROMEOS_SYSTEM_LOGS_SINGLE_LOG_SOURCE_H_