[heap] Do not perform black allocation in memory reducing mode.

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 686c6738821437a1621c4f495391632813ae58e3..2f16ad3af1b3e75a8c7741743d8d2ede61e2c9d1 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -557,7 +557,7 @@ void IncrementalMarking::StartMarking() {
   IncrementalMarkingRootMarkingVisitor visitor(this);
   heap_->IterateStrongRoots(&visitor, VISIT_ONLY_STRONG);
 
-  if (FLAG_black_allocation) {
+  if (FLAG_black_allocation && !heap()->ShouldReduceMemory()) {
     StartBlackAllocation();
   }
 
@@ -583,9 +583,11 @@ void IncrementalMarking::StartBlackAllocation() {
 }
 
 void IncrementalMarking::FinishBlackAllocation() {
-  black_allocation_ = false;
-  if (FLAG_trace_incremental_marking) {
-    PrintF("[IncrementalMarking] Black allocation finished\n");
+  if (black_allocation_) {

[Hannes Payer (out of office), 2016/04/08 11:43:25]

We cannot guarantee that black allocation was on. An explicit GC call after
starting marking may result in a full GC where nothing was allocated black.

+    black_allocation_ = false;
+    if (FLAG_trace_incremental_marking) {
+      PrintF("[IncrementalMarking] Black allocation finished\n");
+    }
   }
 }
 
@@ -759,6 +761,12 @@ void IncrementalMarking::FinalizeIncrementally() {
       (marking_progress <
        FLAG_min_progress_during_incremental_marking_finalization)) {
     finalize_marking_completed_ = true;
+
+    // If black allocation was not enabled earlier, start black allocation
+    // here.
+    if (FLAG_black_allocation && !black_allocation_) {
+      StartBlackAllocation();
+    }
   }
 }