[turbofan] Introduce JSCallForwardVarargs operator.

src/arm/interface-descriptors-arm.cc

Index: src/arm/interface-descriptors-arm.cc
diff --git a/src/arm/interface-descriptors-arm.cc b/src/arm/interface-descriptors-arm.cc
index 506c89103869f8a2a1cd99fc681d80409d066be8..a4fbc2902c847895f59f2d026c9252dea1344bd1 100644
--- a/src/arm/interface-descriptors-arm.cc
+++ b/src/arm/interface-descriptors-arm.cc
@@ -179,6 +179,13 @@ void CallTrampolineDescriptor::InitializePlatformSpecific(
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 
+void CallForwardVarargsDescriptor::InitializePlatformSpecific(
+    CallInterfaceDescriptorData* data) {
+  // r2 : start index (to support rest parameters)
+  // r1 : the target to call
+  Register registers[] = {r1, r2};
+  data->InitializePlatformSpecific(arraysize(registers), registers);
+}
 
 void ConstructStubDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {