[Interpreter] Add support for JS calls.

src/compiler/linkage.h

Index: src/compiler/linkage.h
diff --git a/src/compiler/linkage.h b/src/compiler/linkage.h
index 57203627887647cbaa1736d45292054d121adbbe..226038c23906c71b64c23aabb9621897caf89e82 100644
--- a/src/compiler/linkage.h
+++ b/src/compiler/linkage.h
@@ -124,6 +124,7 @@ class CallDescriptor final : public ZoneObject {
     kHasLocalCatchHandler = 1u << 4,
     kSupportsTailCalls = 1u << 5,
     kCanUseRoots = 1u << 6,
+    kHasVarArgs = 1u << 7,
     kPatchableCallSiteWithNop = kPatchableCallSite | kNeedsNopAfterCall
   };
   typedef base::Flags<Flag> Flags;
@@ -181,10 +182,13 @@ class CallDescriptor final : public ZoneObject {
 
   size_t FrameStateCount() const { return NeedsFrameState() ? 1 : 0; }
 
+  size_t VarArgsInputCount() const { return HasVarArgs() ? 2 : 0; }
+
   Flags flags() const { return flags_; }
 
   bool NeedsFrameState() const { return flags() & kNeedsFrameState; }
   bool SupportsTailCalls() const { return flags() & kSupportsTailCalls; }
+  bool HasVarArgs() const { return flags() & kHasVarArgs; }
 
   LinkageLocation GetReturnLocation(size_t index) const {
     return location_sig_->GetReturn(index);