Change sentinel value for zapping of old-to-new pointers.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index c455564b41a736d268db2e81a9259fec07b261bd..39b0eab172f610f5ea5ec07539b84071c69994a1 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -2738,7 +2738,9 @@ static void UpdatePointer(HeapObject** p, HeapObject* object) {
     // We have to zap this pointer, because the store buffer may overflow later,
     // and then we have to scan the entire heap and we don't want to find
     // spurious newspace pointers in the old space.
-    *p = reinterpret_cast<HeapObject*>(Smi::FromInt(0));
+    // TODO(mstarzinger): This was changed to a sentinel value to track down
+    // rare crashes, change it back to Smi::FromInt(0) later.
+    *p = reinterpret_cast<HeapObject*>(Smi::FromInt(0x0f100d00 >> 1)); // flood
   }
 }