Promote RtcEventLogOutputFile to api/

Preparation for deleting PeerConnectionInterface::StartRtcEventLog
method with a PlatformFile argument.

Bug: webrtc:6463
Change-Id: Ia9fa1d99a3d87f3bf193e73382690b782ffea65c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/135285
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27879}
diff --git a/api/rtc_event_log_output_file.h b/api/rtc_event_log_output_file.h
new file mode 100644
index 0000000..e536dfc
--- /dev/null
+++ b/api/rtc_event_log_output_file.h
@@ -0,0 +1,62 @@
+/*
+ *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef API_RTC_EVENT_LOG_OUTPUT_FILE_H_
+#define API_RTC_EVENT_LOG_OUTPUT_FILE_H_
+
+#include <stddef.h>
+#include <stdio.h>
+#include <string>
+
+#include "api/rtc_event_log_output.h"
+#include "rtc_base/platform_file.h"  // Can't neatly forward PlatformFile.
+#include "rtc_base/system/file_wrapper.h"
+
+namespace webrtc {
+
+class RtcEventLogOutputFile final : public RtcEventLogOutput {
+ public:
+  static const size_t kMaxReasonableFileSize;  // Explanation at declaration.
+
+  // Unlimited/limited-size output file (by filename).
+  explicit RtcEventLogOutputFile(const std::string& file_name);
+  RtcEventLogOutputFile(const std::string& file_name, size_t max_size_bytes);
+
+  // Limited-size output file (by FILE*). This class takes ownership
+  // of the FILE*, and closes it on destruction.
+  RtcEventLogOutputFile(FILE* file, size_t max_size_bytes);
+
+  // TODO(bugs.webrtc.org/6463): Deprecated, delete together with the
+  // corresponding PeerConnection::StartRtcEventLog override.
+  RtcEventLogOutputFile(rtc::PlatformFile file, size_t max_size_bytes);
+
+  ~RtcEventLogOutputFile() override = default;
+
+  bool IsActive() const override;
+
+  bool Write(const std::string& output) override;
+
+ private:
+  RtcEventLogOutputFile(FileWrapper file, size_t max_size_bytes);
+
+  // IsActive() can be called either from outside or from inside, but we don't
+  // want to incur the overhead of a virtual function call if called from inside
+  // some other function of this class.
+  inline bool IsActiveInternal() const;
+
+  // Maximum size, or zero for no limit.
+  const size_t max_size_bytes_;
+  size_t written_bytes_{0};
+  FileWrapper file_;
+};
+
+}  // namespace webrtc
+
+#endif  // API_RTC_EVENT_LOG_OUTPUT_FILE_H_