[heap] Ensure quick progress of incremental marking near OOM.

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 1834 matching lines @@
     return old_generation_allocation_limit_;
   }
 
   bool always_allocate() { return always_allocate_scope_count_.Value() != 0; }
 
   bool CanExpandOldGeneration(int size) {
     if (force_oom_) return false;
     return (OldGenerationCapacity() + size) < MaxOldGenerationSize();
   }
 
+  bool IsCloseToOutOfMemory(size_t slack) {
+    return OldGenerationCapacity() + slack >= MaxOldGenerationSize();
+  }
+
   bool ShouldExpandOldGenerationOnAllocationFailure();
 
   enum class IncrementalMarkingLimit { kNoLimit, kSoftLimit, kHardLimit };
   IncrementalMarkingLimit IncrementalMarkingLimitReached();
 
   // ===========================================================================
   // Idle notification. ========================================================
   // ===========================================================================
 
   bool RecentIdleNotificationHappened();
@@ skipping 774 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_