RC: Add UsageClock::IsInUse().

This method returns true if Chrome is considered to be in use. This
will be used by TabManager to know whether it should schedule a call
to PerformStateTransitions() (it is never necessary to schedule a call
to this method when Chrome is not in use).

Bug: 775644
Change-Id: I20e2e55280c84fcef9b56bb18c2feedb3aed136d
Reviewed-on: https://chromium-review.googlesource.com/1133301Reviewed-by: Sébastien Marchand <sebmarchand@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574216}

chrome/browser/resource_coordinator/usage_clock.cc

@@ -28,23 +28,27 @@ UsageClock::~UsageClock() {
 
 base::TimeDelta UsageClock::GetTotalUsageTime() const {
   base::TimeDelta elapsed_time_in_session = usage_time_in_completed_sessions_;
-  if (!current_usage_session_start_time_.is_null())
+  if (IsInUse())
     elapsed_time_in_session += NowTicks() - current_usage_session_start_time_;
   return elapsed_time_in_session;
 }
 
+bool UsageClock::IsInUse() const {
+  return !current_usage_session_start_time_.is_null();
+}
+
 #if !defined(OS_CHROMEOS)
 void UsageClock::OnSessionStarted(base::TimeTicks session_start) {
   // Ignore |session_start| because it doesn't come from the resource
   // coordinator clock.
-  DCHECK(current_usage_session_start_time_.is_null());
+  DCHECK(!IsInUse());
   current_usage_session_start_time_ = NowTicks();
 }
 
 void UsageClock::OnSessionEnded(base::TimeDelta session_length) {
   // Ignore |session_length| because it wasn't measured using the resource
   // coordinator clock.
-  DCHECK(!current_usage_session_start_time_.is_null());
+  DCHECK(IsInUse());
   usage_time_in_completed_sessions_ +=
       NowTicks() - current_usage_session_start_time_;
   current_usage_session_start_time_ = base::TimeTicks();

chrome/browser/resource_coordinator/usage_clock.h

@@ -38,6 +38,9 @@ class UsageClock
   // Returns the amount of Chrome usage time since this was instantiated.
   base::TimeDelta GetTotalUsageTime() const;
 
+  // Returns true if Chrome is currently considered to be in use.
+  bool IsInUse() const;
+
  private:
 #if !defined(OS_CHROMEOS)
   void OnSessionStarted(base::TimeTicks session_start) override;

chrome/browser/resource_coordinator/usage_clock_unittest.cc

@@ -27,15 +27,13 @@ TEST(ResourceCoordinatorUsageClock, UsageClock) {
 
 #if defined(OS_CHROMEOS)
     // On ChromeOS, UsageClock behaves like a normal clock.
-    UsageClock session_clock;
-    EXPECT_EQ(session_clock.GetTotalUsageTime(), base::TimeDelta());
+    UsageClock usage_clock;
+    EXPECT_EQ(usage_clock.GetTotalUsageTime(), base::TimeDelta());
 
     clock.Advance(base::TimeDelta::FromMinutes(1));
-    EXPECT_EQ(session_clock.GetTotalUsageTime(),
-              base::TimeDelta::FromMinutes(1));
+    EXPECT_EQ(usage_clock.GetTotalUsageTime(), base::TimeDelta::FromMinutes(1));
     clock.Advance(base::TimeDelta::FromMinutes(1));
-    EXPECT_EQ(session_clock.GetTotalUsageTime(),
-              base::TimeDelta::FromMinutes(2));
+    EXPECT_EQ(usage_clock.GetTotalUsageTime(), base::TimeDelta::FromMinutes(2));
 #else
     // On non-ChromeOS, UsageClock advances when
     // DesktopSessionDurationTracker::in_session() is true.
@@ -46,35 +44,34 @@ TEST(ResourceCoordinatorUsageClock, UsageClock) {
     tracker->OnUserEvent();
     EXPECT_TRUE(tracker->in_session());
 
-    UsageClock session_clock;
-    EXPECT_EQ(session_clock.GetTotalUsageTime(), base::TimeDelta());
+    UsageClock usage_clock;
+    EXPECT_EQ(usage_clock.GetTotalUsageTime(), base::TimeDelta());
+    EXPECT_TRUE(tracker->in_session());
+    EXPECT_TRUE(usage_clock.IsInUse());
 
     // Verify that time advances when Chrome is in use.
     clock.Advance(base::TimeDelta::FromMinutes(1));
-    EXPECT_EQ(session_clock.GetTotalUsageTime(),
-              base::TimeDelta::FromMinutes(1));
+    EXPECT_EQ(usage_clock.GetTotalUsageTime(), base::TimeDelta::FromMinutes(1));
     clock.Advance(base::TimeDelta::FromMinutes(1));
-    EXPECT_EQ(session_clock.GetTotalUsageTime(),
-              base::TimeDelta::FromMinutes(2));
+    EXPECT_EQ(usage_clock.GetTotalUsageTime(), base::TimeDelta::FromMinutes(2));
 
     // Verify that time is updated when Chrome stops being used.
     clock.Advance(base::TimeDelta::FromMinutes(1));
     tracker->OnVisibilityChanged(false, base::TimeDelta());
     EXPECT_FALSE(tracker->in_session());
-    EXPECT_EQ(session_clock.GetTotalUsageTime(),
-              base::TimeDelta::FromMinutes(3));
+    EXPECT_FALSE(usage_clock.IsInUse());
+    EXPECT_EQ(usage_clock.GetTotalUsageTime(), base::TimeDelta::FromMinutes(3));
 
     // Verify that time stays still when Chrome is not in use.
     clock.Advance(base::TimeDelta::FromMinutes(1));
-    EXPECT_EQ(session_clock.GetTotalUsageTime(),
-              base::TimeDelta::FromMinutes(3));
+    EXPECT_EQ(usage_clock.GetTotalUsageTime(), base::TimeDelta::FromMinutes(3));
 
     // Verify that time advances again when Chrome is in use.
     tracker->OnVisibilityChanged(true, base::TimeDelta());
     EXPECT_TRUE(tracker->in_session());
+    EXPECT_TRUE(usage_clock.IsInUse());
     clock.Advance(base::TimeDelta::FromMinutes(1));
-    EXPECT_EQ(session_clock.GetTotalUsageTime(),
-              base::TimeDelta::FromMinutes(4));
+    EXPECT_EQ(usage_clock.GetTotalUsageTime(), base::TimeDelta::FromMinutes(4));
 #endif  // defined(OS_CHROMEOS)
   }