[crankshaft] Protect against deopt loops from string length overflows.

src/isolate-inl.h

Index: src/isolate-inl.h
diff --git a/src/isolate-inl.h b/src/isolate-inl.h
index 5c71d9188ec51da408f25b1334e0272abc3359e4..7011c0d35a85f4a064756938ea09d8c713bfabde 100644
--- a/src/isolate-inl.h
+++ b/src/isolate-inl.h
@@ -147,6 +147,11 @@ bool Isolate::IsHasInstanceLookupChainIntact() {
   return has_instance_cell->value() == Smi::FromInt(kArrayProtectorValid);
 }
 
+bool Isolate::IsStringLengthOverflowIntact() {
+  PropertyCell* has_instance_cell = heap()->string_length_protector();
+  return has_instance_cell->value() == Smi::FromInt(kArrayProtectorValid);
+}
+
 }  // namespace internal
 }  // namespace v8