Add unit tests for sub-components of CaptureScheduler.

remoting/base/rate_counter.cc

Index: remoting/base/rate_counter.cc
diff --git a/remoting/base/rate_counter.cc b/remoting/base/rate_counter.cc
index fff9b6cebcd18f3734cf7e5c9ed1c925b36fc1a4..e6532da165541fb06c21cee39032572cf7b8627e 100644
--- a/remoting/base/rate_counter.cc
+++ b/remoting/base/rate_counter.cc
@@ -4,36 +4,43 @@
 
 #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_;
 
@@ -46,4 +53,10 @@ void RateCounter::Evict(base::Time current_time) {
   }
 }
 
+base::Time RateCounter::CurrentTime() const {
+  if (current_time_for_test_ == base::Time())
+    return base::Time::Now();
+  return current_time_for_test_;
+}
+
 }  // namespace remoting