Fix GC bug with missing handle. Bug=133618

src/mips/lithium-codegen-mips.cc

Index: src/mips/lithium-codegen-mips.cc
===================================================================
--- src/mips/lithium-codegen-mips.cc	(revision 11873)
+++ src/mips/lithium-codegen-mips.cc	(working copy)
@@ -2341,15 +2341,14 @@
   } else {
     // Negative lookup.
     // Check prototypes.
-    HeapObject* current = HeapObject::cast((*type)->prototype());
+    Handle<HeapObject> current(HeapObject::cast((*type)->prototype()));
     Heap* heap = type->GetHeap();
-    while (current != heap->null_value()) {
-      Handle<HeapObject> link(current);
-      __ LoadHeapObject(result, link);
+    while (*current != heap->null_value()) {
+      __ LoadHeapObject(result, current);
       __ lw(result, FieldMemOperand(result, HeapObject::kMapOffset));
-      DeoptimizeIf(ne, env,
-          result, Operand(Handle<Map>(JSObject::cast(current)->map())));
-      current = HeapObject::cast(current->map()->prototype());
+      DeoptimizeIf(ne, env, result, Operand(Handle<Map>(current->map())));
+      current =
+          Handle<HeapObject>(HeapObject::cast(current->map()->prototype()));
     }
     __ LoadRoot(result, Heap::kUndefinedValueRootIndex);
   }