Update V8 to r6238 as required by WebKit r75993

Change-Id: I12f638fcdd02d9102abab17d81c23cde63c08f22
diff --git a/src/objects-debug.cc b/src/objects-debug.cc
index 0b83182..a3552c7 100644
--- a/src/objects-debug.cc
+++ b/src/objects-debug.cc
@@ -368,8 +368,10 @@
   } else {
     ASSERT(number->IsSmi());
     int value = Smi::cast(number)->value();
-    ASSERT(value == 0 || value == 1 || value == -1 ||
-           value == -2 || value == -3);
+    // Hidden oddballs have negative smis.
+    const int kLeastHiddenOddballNumber = -4;
+    ASSERT(value <= 1);
+    ASSERT(value >= kLeastHiddenOddballNumber);
   }
 }