Annotate PromotionQueue::RelocateQueueHead for MemorySanitizer.

src/heap/heap.cc

 // 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.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 1365 matching lines @@
   intptr_t* head_end = Min(front_, reinterpret_cast<intptr_t*>(p->area_end()));
 
   int entries_count =
       static_cast<int>(head_end - head_start) / kEntrySizeInWords;
 
   emergency_stack_ = new List<Entry>(2 * entries_count);
 
   while (head_start != head_end) {
     int size = static_cast<int>(*(head_start++));
     HeapObject* obj = reinterpret_cast<HeapObject*>(*(head_start++));
+    // New space allocation in SemiSpaceCopyObject marked the region
+    // overlapping with promotion queue as uninitialized.
+    MSAN_MEMORY_IS_INITIALIZED(&size, sizeof(size));
+    MSAN_MEMORY_IS_INITIALIZED(&obj, sizeof(obj));
     emergency_stack_->Add(Entry(obj, size));
   }
   rear_ = head_end;
 }
 
 
 class ScavengeWeakObjectRetainer : public WeakObjectRetainer {
  public:
   explicit ScavengeWeakObjectRetainer(Heap* heap) : heap_(heap) {}
 
@@ skipping 4745 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 }
 }  // namespace v8::internal