Activate memory reducer for small heaps in background tabs.

src/heap/memory-reducer.cc

Index: src/heap/memory-reducer.cc
diff --git a/src/heap/memory-reducer.cc b/src/heap/memory-reducer.cc
index ee1009134bc75ec9c9ed721ecc3ad0770a34a1d5..f53730785a80fcc3bcd73063f50f7471841fdecd 100644
--- a/src/heap/memory-reducer.cc
+++ b/src/heap/memory-reducer.cc
@@ -47,7 +47,7 @@ void MemoryReducer::TimerTask::RunInternal() {
   event.should_start_incremental_gc = is_idle || optimize_for_memory;
   event.can_start_incremental_gc =
       heap->incremental_marking()->IsStopped() &&
-      heap->incremental_marking()->CanBeActivated();
+      (heap->incremental_marking()->CanBeActivated() || optimize_for_memory);
   memory_reducer_->NotifyTimer(event);
 }
 
@@ -118,9 +118,8 @@ void MemoryReducer::NotifyMarkCompact(const Event& event) {
   }
 }
 
-
-void MemoryReducer::NotifyContextDisposed(const Event& event) {
-  DCHECK_EQ(kContextDisposed, event.type);
+void MemoryReducer::NotifyPossibleGarbage(const Event& event) {
+  DCHECK_EQ(kPossibleGarbage, event.type);
   Action old_action = state_.action;
   state_ = Step(state_, event);
   if (old_action != kWait && state_.action == kWait) {
@@ -147,14 +146,14 @@ MemoryReducer::State MemoryReducer::Step(const State& state,
       if (event.type == kTimer) {
         return state;
       } else {
-        DCHECK(event.type == kContextDisposed || event.type == kMarkCompact);
+        DCHECK(event.type == kPossibleGarbage || event.type == kMarkCompact);
         return State(
             kWait, 0, event.time_ms + kLongDelayMs,
             event.type == kMarkCompact ? event.time_ms : state.last_gc_time_ms);
       }
     case kWait:
       switch (event.type) {
-        case kContextDisposed:
+        case kPossibleGarbage:
           return state;
         case kTimer:
           if (state.started_gcs >= kMaxNumberOfGCs) {