Add unit tests for sub-components of CaptureScheduler.

remoting/base/rate_counter.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "remoting/base/rate_counter.h"
 
+#include "base/logging.h"
+
 namespace remoting {
 
 RateCounter::RateCounter(base::TimeDelta time_window)
     : time_window_(time_window),
       sum_(0) {
+  DCHECK_GT(time_window.InMilliseconds(), 0);
 }
 
 RateCounter::~RateCounter() {
 }
 
 void RateCounter::Record(int64 value) {
-  base::Time current_time = base::Time::Now();
-  Evict(current_time);
+  DCHECK(CalledOnValidThread());
 
-  base::AutoLock auto_lock(lock_);
+  base::Time current_time = CurrentTime();
+  EvictOldDataPoints(current_time);
   sum_ += value;
   data_points_.push(std::make_pair(current_time, value));
 }
 
 double RateCounter::Rate() {
-  Evict(base::Time::Now());
+  DCHECK(CalledOnValidThread());
 
-  base::AutoLock auto_lock(lock_);
-  return static_cast<double>(base::Time::kMillisecondsPerSecond) * sum_ /
-      time_window_.InMilliseconds();
+  EvictOldDataPoints(CurrentTime());
+  return sum_ / time_window_.InSecondsF();
 }
 
-void RateCounter::Evict(base::Time current_time) {
-  base::AutoLock auto_lock(lock_);
+void RateCounter::SetCurrentTimeForTest(base::Time current_time) {
+  DCHECK(CalledOnValidThread());
+  DCHECK(current_time >= current_time_for_test_);
 
+  current_time_for_test_ = current_time;
+}
+
+void RateCounter::EvictOldDataPoints(base::Time current_time) {
   // Remove data points outside of the window.
   base::Time window_start = current_time - time_window_;
 
   while (!data_points_.empty()) {
     if (data_points_.front().first > window_start)
       break;
 
     sum_ -= data_points_.front().second;
     data_points_.pop();
   }
 }
 
+base::Time RateCounter::CurrentTime() const {
+  if (current_time_for_test_ == base::Time())
+    return base::Time::Now();
+  return current_time_for_test_;
+}
+
 }  // namespace remoting