[turbofan] Introduce JSCallForwardVarargs operator.

src/interface-descriptors.h

Index: src/interface-descriptors.h
diff --git a/src/interface-descriptors.h b/src/interface-descriptors.h
index 1d1b48af93a0b4ab780f021beb69481897af625c..315379d5ddc9a8eb5bfd7bb55f7d866e417770a3 100644
--- a/src/interface-descriptors.h
+++ b/src/interface-descriptors.h
@@ -46,6 +46,7 @@ class PlatformInterfaceDescriptor;
   V(CallFunction)                         \
   V(CallFunctionWithFeedback)             \
   V(CallFunctionWithFeedbackAndVector)    \
+  V(CallForwardVarargs)                   \
   V(CallConstruct)                        \
   V(CallTrampoline)                       \
   V(ConstructStub)                        \
@@ -560,6 +561,12 @@ class CallTrampolineDescriptor : public CallInterfaceDescriptor {
                                                CallInterfaceDescriptor)
 };
 
+class CallForwardVarargsDescriptor : public CallInterfaceDescriptor {
+ public:
+  DEFINE_PARAMETERS(kTarget, kStartIndex)
+  DECLARE_DESCRIPTOR_WITH_CUSTOM_FUNCTION_TYPE(CallForwardVarargsDescriptor,
+                                               CallInterfaceDescriptor)
+};
 
 class ConstructStubDescriptor : public CallInterfaceDescriptor {
  public: