[ic] Cache weak cells containing prototypes in respective PrototypeInfo objects.

src/objects-debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/objects.h"
 
 #include "src/bootstrapper.h"
 #include "src/disasm.h"
 #include "src/disassembler.h"
 #include "src/field-type.h"
@@ skipping 959 matching lines @@
         (instantiated() && evaluated() && code()->IsModuleInfo()));
 
   CHECK(module_namespace()->IsUndefined(GetIsolate()) ||
         module_namespace()->IsJSModuleNamespace());
 
   // TODO(neis): Check more.
 }
 
 void PrototypeInfo::PrototypeInfoVerify() {
   CHECK(IsPrototypeInfo());
+  CHECK(weak_cell()->IsWeakCell() || weak_cell()->IsUndefined(GetIsolate()));
   if (prototype_users()->IsWeakFixedArray()) {
     WeakFixedArray::cast(prototype_users())->FixedArrayVerify();
   } else {
     CHECK(prototype_users()->IsSmi());
   }
   CHECK(validity_cell()->IsCell() || validity_cell()->IsSmi());
 }
 
 void Tuple3::Tuple3Verify() {
   CHECK(IsTuple3());
@@ skipping 423 matching lines @@
 
   // Both are done at the same time.
   CHECK_EQ(new_it.done(), old_it.done());
 }
 
 
 #endif  // DEBUG
 
 }  // namespace internal
 }  // namespace v8