Fixing bogus assertion.

src/incremental-marking.cc

Index: src/incremental-marking.cc
diff --git a/src/incremental-marking.cc b/src/incremental-marking.cc
index 95642e90f19d11b3212bc37013ec46433da9701c..6cb7aa4858d80ca1e096a14b06d862a3a1b8e46a 100644
--- a/src/incremental-marking.cc
+++ b/src/incremental-marking.cc
@@ -67,7 +67,9 @@ void IncrementalMarking::RecordWriteFromCode(HeapObject* obj,
   // Fast cases should already be covered by RecordWriteStub.
   ASSERT(value->IsHeapObject());
   ASSERT(!value->IsHeapNumber());
-  ASSERT(!value->IsString() || value->IsConsString());
+  ASSERT(!value->IsString() ||
+         value->IsConsString() ||
+         value->IsSlicedString());
   ASSERT(Marking::IsWhite(Marking::MarkBitFrom(HeapObject::cast(value))));
 
   IncrementalMarking* marking = isolate->heap()->incremental_marking();