Add a histogram metric tracking for how long audio RTP packets are sent

webrtc/rtc_base/time_interval_unittest.cc

Index: webrtc/rtc_base/time_interval_unittest.cc
diff --git a/webrtc/rtc_base/time_interval_unittest.cc b/webrtc/rtc_base/time_interval_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..69ba30520d1f52329d757084dd88804be3dbb541
--- /dev/null
+++ b/webrtc/rtc_base/time_interval_unittest.cc
@@ -0,0 +1,49 @@
+/*
+ *  Copyright 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.
+ */
+
+#include "webrtc/rtc_base/time_interval.h"
+#include "webrtc/rtc_base/thread.h"
+#include "webrtc/test/gtest.h"
+
+namespace rtc {
+
+TEST(TimeIntervalTest, TimeInMs) {
+  TimeInterval interval;
+  interval.Extend();
+  Thread::SleepMs(100);

[ossu, 2017/07/14 11:13:15]

Use a fake clock for testing instead. This is prone to going flaky (and will
make the test always take more time than strictly necessary).

With the fake timer, you should be able to make the test below even stricter:
e.g. if 100 ms has elapsed, make sure the interval reports exactly 100 ms and
not 99 or 101.

[saza WebRTC, 2017/07/17 14:27:29]

Done.

+  interval.Extend();
+  // Allow for the thread to wakeup ~20ms early.
+  EXPECT_GE(*interval.Last(), *interval.First() + 80);
+  // Make sure the Time is not returning in smaller unit like microseconds.
+  EXPECT_LT(*interval.Last(), *interval.First() + 1000);
+}
+
+TEST(TimeIntervalTest, Empty) {
+  TimeInterval interval;
+  EXPECT_TRUE(interval.Empty());
+  interval.Extend();
+  EXPECT_FALSE(interval.Empty());
+  interval.Extend(200);
+  EXPECT_FALSE(interval.Empty());
+}
+
+TEST(TimeIntervalTest, MonotoneIncreasing) {
+  const size_t point_count = 7;
+  const int64_t interval_points[] = {3, 2, 5, 0, 4, 1, 6};
+  const int64_t interval_differences[] = {0, 1, 3, 5, 5, 5, 6};
+  TimeInterval interval;
+  EXPECT_FALSE(interval.First());
+  for (size_t i = 0; i < point_count; ++i) {
+    interval.Extend(interval_points[i]);
+    EXPECT_EQ(interval_differences[i], *interval.Last() - *interval.First());
+  }
+}
+
+}  // namespace rtc