RC: Add LifecycleUnit::GetStateChangeTime().

This method the last time at which the state of a LifecycleUnit
changed. It will be used to determine if a LifeycleUnit has been
unfrozen long enough and should be frozen again.

Bug: 775644
Change-Id: I2ba04b9ed4085767e67108cd46901d876efc2217
Reviewed-on: https://chromium-review.googlesource.com/1134029
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: Sébastien Marchand <sebmarchand@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575067}

chrome/browser/resource_coordinator/lifecycle_unit.h

@@ -120,6 +120,9 @@ class LifecycleUnit {
   // Returns the current state of this LifecycleUnit.
   virtual LifecycleUnitState GetState() const = 0;
 
+  // Returns the last time at which the state of this LifecycleUnit changed.
+  virtual base::TimeTicks GetStateChangeTime() const = 0;
+
   // Request that the LifecycleUnit be loaded, return true if the request is
   // successful.
   virtual bool Load() = 0;

chrome/browser/resource_coordinator/lifecycle_unit_base.cc

@@ -30,6 +30,10 @@ LifecycleUnitState LifecycleUnitBase::GetState() const {
   return state_;
 }
 
+base::TimeTicks LifecycleUnitBase::GetStateChangeTime() const {
+  return state_change_time_;
+}
+
 base::TimeTicks LifecycleUnitBase::GetWallTimeWhenHidden() const {
   return wall_time_when_hidden_;
 }
@@ -56,6 +60,7 @@ void LifecycleUnitBase::SetState(LifecycleUnitState state,
     return;
   LifecycleUnitState last_state = state_;
   state_ = state;
+  state_change_time_ = NowTicks();
   OnLifecycleUnitStateChanged(last_state, reason);
   for (auto& observer : observers_)
     observer.OnLifecycleUnitStateChanged(this, last_state);

chrome/browser/resource_coordinator/lifecycle_unit_base.h

@@ -8,6 +8,7 @@
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "chrome/browser/resource_coordinator/lifecycle_unit.h"
+#include "chrome/browser/resource_coordinator/time.h"
 #include "content/public/browser/visibility.h"
 
 namespace resource_coordinator {
@@ -29,6 +30,7 @@ class LifecycleUnitBase : public LifecycleUnit {
   base::TimeTicks GetWallTimeWhenHidden() const override;
   base::TimeDelta GetChromeUsageTimeWhenHidden() const override;
   LifecycleUnitState GetState() const override;
+  base::TimeTicks GetStateChangeTime() const override;
   void AddObserver(LifecycleUnitObserver* observer) override;
   void RemoveObserver(LifecycleUnitObserver* observer) override;
   ukm::SourceId GetUkmSourceId() const override;
@@ -64,6 +66,9 @@ class LifecycleUnitBase : public LifecycleUnit {
   // Current state of this LifecycleUnit.
   LifecycleUnitState state_ = LifecycleUnitState::ACTIVE;
 
+  // Time at which the state changed.
+  base::TimeTicks state_change_time_ = NowTicks();
+
   // The wall time when this LifecycleUnit was last hidden, or TimeDelta::Max()
   // if this LifecycleUnit is currently visible.
   base::TimeTicks wall_time_when_hidden_;

chrome/browser/resource_coordinator/lifecycle_unit_base_unittest.cc

@@ -72,6 +72,28 @@ TEST_F(LifecycleUnitBaseTest, GetID) {
   EXPECT_EQ(c.GetID(), c.GetID());
 }
 
+// Verify that the state change time is updated when the state changes.
+TEST_F(LifecycleUnitBaseTest, SetStateUpdatesTime) {
+  TestLifecycleUnit lifecycle_unit;
+  EXPECT_EQ(NowTicks(), lifecycle_unit.GetStateChangeTime());
+
+  test_clock_.Advance(base::TimeDelta::FromSeconds(1));
+  base::TimeTicks first_state_change_time = NowTicks();
+  lifecycle_unit.SetState(LifecycleUnitState::DISCARDED,
+                          LifecycleUnitStateChangeReason::BROWSER_INITIATED);
+  EXPECT_EQ(first_state_change_time, lifecycle_unit.GetStateChangeTime());
+  test_clock_.Advance(base::TimeDelta::FromSeconds(1));
+  EXPECT_EQ(first_state_change_time, lifecycle_unit.GetStateChangeTime());
+
+  test_clock_.Advance(base::TimeDelta::FromSeconds(1));
+  base::TimeTicks second_state_change_time = NowTicks();
+  lifecycle_unit.SetState(LifecycleUnitState::FROZEN,
+                          LifecycleUnitStateChangeReason::BROWSER_INITIATED);
+  EXPECT_EQ(second_state_change_time, lifecycle_unit.GetStateChangeTime());
+  test_clock_.Advance(base::TimeDelta::FromSeconds(1));
+  EXPECT_EQ(second_state_change_time, lifecycle_unit.GetStateChangeTime());
+}
+
 // Verify that observers are notified when the state changes and when the
 // LifecycleUnit is destroyed.
 TEST_F(LifecycleUnitBaseTest, SetStateNotifiesObservers) {