This fixes missing incremental write barrier issue when double fields unboxing is enabled.

src/heap/spaces.h

 // Copyright 2011 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_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include "src/allocation.h"
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
@@ skipping 367 matching lines @@
     // WAS_SWEPT indicates that marking bits have been cleared by the sweeper,
     // otherwise marking bits are still intact.
     WAS_SWEPT,
 
     // Large objects can have a progress bar in their page header. These object
     // are scanned in increments and will be kept black while being scanned.
     // Even if the mutator writes to them they will be kept black and a white
     // to grey transition is performed in the value.
     HAS_PROGRESS_BAR,
 
+    // This flag is intended to be used for testing. Works only when both
+    // FLAG_stress_compaction and FLAG_manual_evacuation_candidates_selection
+    // are set. It forces the page to become an evacuation candidate at next
+    // candidates selection cycle.
+    FORCE_EVACUATION_CANDIDATE_FOR_TESTING,
+
     // Last flag, keep at bottom.
     NUM_MEMORY_CHUNK_FLAGS
   };
 
 
   static const int kPointersToHereAreInterestingMask =
       1 << POINTERS_TO_HERE_ARE_INTERESTING;
 
   static const int kPointersFromHereAreInterestingMask =
       1 << POINTERS_FROM_HERE_ARE_INTERESTING;
@@ skipping 2466 matching lines @@
     count = 0;
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_SPACES_H_