[interpreter] Update ForInPrepare to conditionally use runtime.

src/code-stub-assembler.h

 // Copyright 2016 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_STUB_ASSEMBLER_H_
 #define V8_CODE_STUB_ASSEMBLER_H_
 
 #include <functional>
 
 #include "src/compiler/code-assembler.h"
@@ skipping 456 matching lines @@
                               compiler::Node* map, Label* if_handler,
                               Variable* var_handler, Label* if_miss);
 
   void TryProbeStubCache(StubCache* stub_cache, compiler::Node* receiver,
                          compiler::Node* name, Label* if_handler,
                          Variable* var_handler, Label* if_miss);
 
   void LoadIC(const LoadICParameters* p);
   void LoadGlobalIC(const LoadICParameters* p);
 
+  // Get the enumerable length from |map| and return the result as a Smi.
+  compiler::Node* EnumLength(compiler::Node* map);
+
+  // Check the cache validity for |receiver|. Branch to |use_cache| if
+  // the cache is valid, otherwise branch to |use_runtime|.
+  void CheckEnumCache(compiler::Node* receiver,
+                      CodeStubAssembler::Label* use_cache,
+                      CodeStubAssembler::Label* use_runtime);
+
  private:
   compiler::Node* ElementOffsetFromIndex(compiler::Node* index,
                                          ElementsKind kind, ParameterMode mode,
                                          int base_size = 0);
 
   compiler::Node* AllocateRawAligned(compiler::Node* size_in_bytes,
                                      AllocationFlags flags,
                                      compiler::Node* top_address,
                                      compiler::Node* limit_address);
   compiler::Node* AllocateRawUnaligned(compiler::Node* size_in_bytes,
                                        AllocationFlags flags,
                                        compiler::Node* top_adddress,
                                        compiler::Node* limit_address);
 
   static const int kElementLoopUnrollThreshold = 8;
 };
 
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_CODE_STUB_ASSEMBLER_H_