[Interpreter] Add ForInPrepare runtime function which returns a ObjectTriple.

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index 21e21356bb6b6407ea4ee1546a9208a1e432533e..1e1c5c7fc907b0d5057afdb881eec0d3e7606c87 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -1746,10 +1746,8 @@ class CEntryStub : public PlatformCodeStub {
       : PlatformCodeStub(isolate) {
     minor_key_ = SaveDoublesBits::encode(save_doubles == kSaveFPRegs) |
                  ArgvMode::encode(argv_mode == kArgvInRegister);
-    DCHECK(result_size == 1 || result_size == 2);
-#if _WIN64 || V8_TARGET_ARCH_PPC
+    DCHECK(result_size == 1 || result_size == 2 || result_size == 3);
     minor_key_ = ResultSizeBits::update(minor_key_, result_size);
-#endif  // _WIN64
   }
 
   // The version of this stub that doesn't save doubles is generated ahead of
@@ -1761,9 +1759,7 @@ class CEntryStub : public PlatformCodeStub {
  private:
   bool save_doubles() const { return SaveDoublesBits::decode(minor_key_); }
   bool argv_in_register() const { return ArgvMode::decode(minor_key_); }
-#if _WIN64 || V8_TARGET_ARCH_PPC
   int result_size() const { return ResultSizeBits::decode(minor_key_); }
-#endif  // _WIN64
 
   bool NeedsImmovableCode() override;