Added log messages for important call setup events: first packet sent/received

webrtc/base/onetimeevent.h

Index: webrtc/base/onetimeevent.h
diff --git a/webrtc/base/onetimeevent.h b/webrtc/base/onetimeevent.h
new file mode 100644
index 0000000000000000000000000000000000000000..9708b4ba0ba05a8dea3664d7ed9ca94fb6cbade7
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+++ b/webrtc/base/onetimeevent.h
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+/*
+ *  Copyright (c) 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_ONETIMEEVENT_H_
+#define WEBRTC_BASE_ONETIMEEVENT_H_
+
+#include "webrtc/base/scoped_ptr.h"
+#include "webrtc/base/criticalsection.h"
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+// Provides a simple way to perform an operation (such as logging) one
+// time in a certain scope.
+// Example:
+//   OneTimeEvent firstFrame;
+//   ...
+//   if (firstFrame()) {
+//     LOG(LS_INFO) << "This is the first frame".
+//   }
+class OneTimeEvent {
+ public:
+  OneTimeEvent() {}
+  bool operator()() {
+    rtc::CritScope cs(&critsect_);
+    if (happened_) {
+      return false;
+    }
+    happened_ = true;
+    return true;
+  }
+
+ private:
+  bool happened_ = false;
+  rtc::CriticalSection critsect_;
+};
+
+// A non-thread-safe, ligher-weight version of the OneTimeEvent class.
+class ThreadUnsafeOneTimeEvent {
+ public:
+  ThreadUnsafeOneTimeEvent() {}
+  bool operator()() {
+    if (happened_) {
+      return false;
+    }
+    happened_ = true;
+    return true;
+  }
+
+ private:
+  bool happened_ = false;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_BASE_ONETIMEEVENT_H_