[TM] Unfreeze a tab if it opt-out while frozen.

This is unlikely to happen in practice, but there's still a tiny race
possibility that could cause this if we ever decide to immediately
freeze tabs after they're being sent to background.

Change-Id: I33fbd9f31692e3e1c8c2c269da01f83c9d672363
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1869721
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Auto-Submit: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709457}

chrome/browser/resource_coordinator/tab_lifecycle_unit.cc

@@ -421,6 +421,14 @@ void TabLifecycleUnitSource::TabLifecycleUnit::UpdateOriginTrialFreezePolicy(
     performance_manager::mojom::InterventionPolicy policy) {
   // The origin trial policy should only be updated when its value changes.
   DCHECK_NE(policy, origin_trial_freeze_policy_);
+  // Unfreeze the tab if needed. This can happen if the tab gets frozen
+  // before all its frames are loaded and if one of these frames
+  // causes the tab to be opted out.
+  if (policy == performance_manager::mojom::InterventionPolicy::kOptOut &&
+      IsFrozenOrPendingFreeze(GetState())) {
+    Unfreeze();
+  }
+
   origin_trial_freeze_policy_ = policy;
 }
 

chrome/browser/resource_coordinator/tab_lifecycle_unit_unittest.cc

@@ -955,4 +955,33 @@ TEST_F(TabLifecycleUnitTest, TabUnfreezeOnIndexedDBLockAcquisition) {
   tab_lifecycle_unit.SetIsHoldingIndexedDBLock(false);
 }
 
+TEST_F(TabLifecycleUnitTest, TabUnfreezeOnOriginTrialOptOut) {
+  TabLifecycleUnit tab_lifecycle_unit(GetTabLifecycleUnitSource(), &observers_,
+                                      usage_clock_.get(), web_contents_,
+                                      tab_strip_model_.get());
+  TabLoadTracker::Get()->TransitionStateForTesting(web_contents_,
+                                                   LoadingState::LOADED);
+  // Advance time enough that the tab is urgent discardable.
+  test_clock_.Advance(kBackgroundUrgentProtectionTime);
+  ExpectCanDiscardTrueAllReasons(&tab_lifecycle_unit);
+
+  DecisionDetails decision_details;
+  EXPECT_TRUE(tab_lifecycle_unit.CanFreeze(&decision_details));
+
+  // Freeze the tab.
+  EXPECT_CALL(observer_, OnFrozenStateChange(web_contents_, true));
+  tab_lifecycle_unit.Freeze();
+  ::testing::Mock::VerifyAndClear(&observer_);
+  EXPECT_EQ(LifecycleUnitState::PENDING_FREEZE, tab_lifecycle_unit.GetState());
+
+  // Indicates that the tab opted out from the Freeze policy via Origin Trial,
+  // this should unfreeze it.
+  EXPECT_CALL(observer_, OnFrozenStateChange(web_contents_, false));
+  tab_lifecycle_unit.UpdateOriginTrialFreezePolicy(
+      performance_manager::mojom::InterventionPolicy::kOptOut);
+  ::testing::Mock::VerifyAndClear(&observer_);
+  EXPECT_EQ(LifecycleUnitState::PENDING_UNFREEZE,
+            tab_lifecycle_unit.GetState());
+}
+
 }  // namespace resource_coordinator