Activate memory reducer for small heaps in background tabs.

src/heap/incremental-marking.cc

Index: src/heap/incremental-marking.cc
diff --git a/src/heap/incremental-marking.cc b/src/heap/incremental-marking.cc
index e082a24441b518be37cab47ab4f7bf34e8d427fa..47595a8905fa576edc514f812574e78341dee143 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -443,7 +443,16 @@ void IncrementalMarking::ActivateIncrementalWriteBarrier() {
 
 
 bool IncrementalMarking::ShouldActivateEvenWithoutIdleNotification() {
+#ifndef DEBUG
+  static const intptr_t kActivationThreshold = 8 * MB;
+#else
+  // TODO(gc) consider setting this to some low level so that some
+  // debug tests run with incremental marking and some without.
+  static const intptr_t kActivationThreshold = 0;
+#endif
+  // Don't switch on for very small heaps.
   return CanBeActivated() &&
+         heap_->PromotedSpaceSizeOfObjects() > kActivationThreshold &&
          heap_->HeapIsFullEnoughToStartIncrementalMarking(
              heap_->old_generation_allocation_limit());
 }
@@ -453,21 +462,12 @@ bool IncrementalMarking::WasActivated() { return was_activated_; }
 
 
 bool IncrementalMarking::CanBeActivated() {
-#ifndef DEBUG
-  static const intptr_t kActivationThreshold = 8 * MB;
-#else
-  // TODO(gc) consider setting this to some low level so that some
-  // debug tests run with incremental marking and some without.
-  static const intptr_t kActivationThreshold = 0;
-#endif
   // Only start incremental marking in a safe state: 1) when incremental
   // marking is turned on, 2) when we are currently not in a GC, and
   // 3) when we are currently not serializing or deserializing the heap.
-  // Don't switch on for very small heaps.
   return FLAG_incremental_marking && heap_->gc_state() == Heap::NOT_IN_GC &&
          heap_->deserialization_complete() &&
-         !heap_->isolate()->serializer_enabled() &&
-         heap_->PromotedSpaceSizeOfObjects() > kActivationThreshold;
+         !heap_->isolate()->serializer_enabled();
 }