Adjust last_visibility_change_time implementation

In this CL, last_visibility_change_time is set to NowTicks() in the constructor. In addition, it is updated prior to notifying observers. This is done so that in proactive tab discarding, when a LifecycleUnit becomes HIDDEN, TabManager knows when it became HIDDEN (now), not the last time it became VISIBLE.

Bug: 77564
Change-Id: Ie909b4a884a7d70b5f542be7588e9fa03eb2fec7
Reviewed-on: https://chromium-review.googlesource.com/1020444
Commit-Queue: Varun Mohan <varunmohan@google.com>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552409}

chrome/browser/resource_coordinator/lifecycle_unit_base.cc

@@ -9,7 +9,8 @@
 
 namespace resource_coordinator {
 
-LifecycleUnitBase::LifecycleUnitBase() = default;
+LifecycleUnitBase::LifecycleUnitBase()
+    : last_visibility_change_time_(NowTicks()) {}
 
 LifecycleUnitBase::~LifecycleUnitBase() = default;
 
@@ -43,9 +44,9 @@ void LifecycleUnitBase::SetState(State state) {
 
 void LifecycleUnitBase::OnLifecycleUnitVisibilityChanged(
     content::Visibility visibility) {
+  last_visibility_change_time_ = NowTicks();
   for (auto& observer : observers_)
     observer.OnLifecycleUnitVisibilityChanged(this, visibility);
-  last_visibility_change_time_ = NowTicks();
 }
 
 void LifecycleUnitBase::OnLifecycleUnitDestroyed() {

chrome/browser/resource_coordinator/lifecycle_unit_base_unittest.cc

@@ -126,6 +126,7 @@ TEST(LifecycleUnitBaseTest, VisibilityChangeNotifiesObserversAndUpdatesTime) {
         EXPECT_EQ(NowTicks(), lifecycle_unit->GetLastVisibilityChangeTime());
       }));
 
+  test_clock_.Advance(base::TimeDelta::FromMinutes(1));
   lifecycle_unit.OnLifecycleUnitVisibilityChanged(content::Visibility::HIDDEN);
   testing::Mock::VerifyAndClear(&observer);
 
@@ -136,6 +137,7 @@ TEST(LifecycleUnitBaseTest, VisibilityChangeNotifiesObserversAndUpdatesTime) {
         EXPECT_EQ(NowTicks(), lifecycle_unit->GetLastVisibilityChangeTime());
       }));
 
+  test_clock_.Advance(base::TimeDelta::FromMinutes(1));
   lifecycle_unit.OnLifecycleUnitVisibilityChanged(
       content::Visibility::OCCLUDED);
   testing::Mock::VerifyAndClear(&observer);
@@ -147,6 +149,7 @@ TEST(LifecycleUnitBaseTest, VisibilityChangeNotifiesObserversAndUpdatesTime) {
         EXPECT_EQ(NowTicks(), lifecycle_unit->GetLastVisibilityChangeTime());
       }));
 
+  test_clock_.Advance(base::TimeDelta::FromMinutes(1));
   lifecycle_unit.OnLifecycleUnitVisibilityChanged(content::Visibility::VISIBLE);
   testing::Mock::VerifyAndClear(&observer);