Fix inobject slack tracking for both subclassing and non-subclassing cases.

src/code-stubs.h

 // 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.
 
 #ifndef V8_CODE_STUBS_H_
 #define V8_CODE_STUBS_H_
 
 #include "src/allocation.h"
 #include "src/assembler.h"
 #include "src/codegen.h"
@@ skipping 2425 matching lines @@
   DEFINE_PLATFORM_CODE_STUB(DoubleToI, PlatformCodeStub);
 };
 
 
 class ScriptContextFieldStub : public HandlerStub {
  public:
   ScriptContextFieldStub(Isolate* isolate,
                          const ScriptContextTable::LookupResult* lookup_result)
       : HandlerStub(isolate) {
     DCHECK(Accepted(lookup_result));
+    STATIC_ASSERT(kContextIndexBits + kSlotIndexBits <= kSubMinorKeyBits);
     set_sub_minor_key(ContextIndexBits::encode(lookup_result->context_index) |
                       SlotIndexBits::encode(lookup_result->slot_index));
   }
 
   int context_index() const {
     return ContextIndexBits::decode(sub_minor_key());
   }
 
   int slot_index() const { return SlotIndexBits::decode(sub_minor_key()); }
 
   static bool Accepted(const ScriptContextTable::LookupResult* lookup_result) {
     return ContextIndexBits::is_valid(lookup_result->context_index) &&
            SlotIndexBits::is_valid(lookup_result->slot_index);
   }
 
  private:
-  static const int kContextIndexBits = 13;
+  static const int kContextIndexBits = 9;
   static const int kSlotIndexBits = 13;
   class ContextIndexBits : public BitField<int, 0, kContextIndexBits> {};
   class SlotIndexBits
       : public BitField<int, kContextIndexBits, kSlotIndexBits> {};
 
   Code::StubType GetStubType() const override { return Code::FAST; }
 
   DEFINE_CODE_STUB_BASE(ScriptContextFieldStub, HandlerStub);
 };
 
@@ skipping 591 matching lines @@
 #undef DEFINE_HYDROGEN_CODE_STUB
 #undef DEFINE_CODE_STUB
 #undef DEFINE_CODE_STUB_BASE
 
 extern Representation RepresentationFromType(Type* type);
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CODE_STUBS_H_