Adding more detail to MessageQueue::Dispatch logging.

webrtc/base/location.h

+/*
+ *  Copyright 2016 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 WEBRTC_BASE_LOCATION_H_
+#define WEBRTC_BASE_LOCATION_H_
+
+#include <string>
+
+#include "webrtc/system_wrappers/include/stringize_macros.h"
+
+namespace rtc {
+
+// Location provides basic info where of an object was constructed, or was
+// significantly brought to life.
+// This is a stripped down version of:
+// https://code.google.com/p/chromium/codesearch#chromium/src/base/location.h
+class Location {
+ public:
+  // Constructor should be called with a long-lived char*, such as __FILE__.
+  // It assumes the provided value will persist as a global constant, and it
+  // will not make a copy of it.
+  //
+  // TODO(deadbeef): Tracing is currently limited to 2 arguments, which is
+  // why the file name and line number are combined into one argument.
+  //
+  // Once TracingV2 is available, separate the file name and line number.
+  Location(const char* function_name, const char* file_and_line);
+  Location();
+  Location(const Location& other);
+  Location& operator=(const Location& other);
+
+  const char* function_name() const { return function_name_; }
+  const char* file_and_line() const { return file_and_line_; }
+
+  std::string ToString() const;
+
+ private:
+  const char* function_name_;
+  const char* file_and_line_;
+};
+
+// Define a macro to record the current source location.
+#define RTC_FROM_HERE RTC_FROM_HERE_WITH_FUNCTION(__FUNCTION__)
+
+#define RTC_FROM_HERE_WITH_FUNCTION(function_name) \
+  ::rtc::Location(function_name, __FILE__ ":" STRINGIZE(__LINE__))
+
+}  // namespace rtc
+
+#endif  // WEBRTC_BASE_LOCATION_H_