From 799379e8c29793b9f681e61dbd1075481b77359a Mon Sep 17 00:00:00 2001
From: asapersson <asapersson@webrtc.org>
Date: Tue, 2 Feb 2016 01:46:53 -0800
Subject: [PATCH] Let a minimum time interval pass (one bucket size) after
 initialization before reporting rates (to avoid rates being based on too
 short time intervals).

BUG=chromium:570038

Review URL: https://codereview.webrtc.org/1582333008

Cr-Commit-Position: refs/heads/master@{#11455}
---
 webrtc/base/ratetracker.cc          |  4 ++++
 webrtc/base/ratetracker_unittest.cc | 12 +++++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/webrtc/base/ratetracker.cc b/webrtc/base/ratetracker.cc
index 35521a8d3d..c1ad2d5e84 100644
--- a/webrtc/base/ratetracker.cc
+++ b/webrtc/base/ratetracker.cc
@@ -63,6 +63,10 @@ double RateTracker::ComputeRateForInterval(
     milliseconds_to_skip = 0u;
     available_interval_milliseconds =
         TimeDiff(current_time, initialization_time_milliseconds_);
+    // Let one bucket interval pass after initialization before reporting.
+    if (available_interval_milliseconds < bucket_milliseconds_) {
+      return 0.0;
+    }
   }
   // If we're skipping all buckets that means that there have been no samples
   // within the sampling interval so report 0.
diff --git a/webrtc/base/ratetracker_unittest.cc b/webrtc/base/ratetracker_unittest.cc
index 2187282cd3..75fec55818 100644
--- a/webrtc/base/ratetracker_unittest.cc
+++ b/webrtc/base/ratetracker_unittest.cc
@@ -12,10 +12,13 @@
 #include "webrtc/base/ratetracker.h"
 
 namespace rtc {
+namespace {
+  const uint32_t kBucketIntervalMs = 100;
+}  // namespace
 
 class RateTrackerForTest : public RateTracker {
  public:
-  RateTrackerForTest() : RateTracker(100u, 10u), time_(0) {}
+  RateTrackerForTest() : RateTracker(kBucketIntervalMs, 10u), time_(0) {}
   virtual uint32_t Time() const { return time_; }
   void AdvanceTime(uint32_t delta) { time_ += delta; }
 
@@ -55,8 +58,11 @@ TEST(RateTrackerTest, TestRateTrackerBasics) {
 
   // Add a sample.
   tracker.AddSamples(1234);
-  // Advance the clock by 100 ms.
-  tracker.AdvanceTime(100);
+  // Advance the clock by less than one bucket interval (no rate returned).
+  tracker.AdvanceTime(kBucketIntervalMs - 1);
+  EXPECT_DOUBLE_EQ(0.0, tracker.ComputeRate());
+  // Advance the clock by 100 ms (one bucket interval).
+  tracker.AdvanceTime(1);
   EXPECT_DOUBLE_EQ(12340.0, tracker.ComputeRateForInterval(1000u));
   EXPECT_DOUBLE_EQ(12340.0, tracker.ComputeRate());
   EXPECT_EQ(1234U, tracker.TotalSampleCount());