[wasm] Support validation of asm.js modules with != 3 args.

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 64c2ec8f3bac642c6f0136fde8476fdc326b9364..fd6ef769afba7ee439b701d016e74b561161b3f7 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -703,7 +703,9 @@ void MacroAssembler::CallRuntime(const Runtime::Function* f,
   // arguments passed in because it is constant. At some point we
   // should remove this need and make the runtime routine entry code
   // smarter.
-  Set(rax, num_arguments);
+  if (num_arguments >= 0) {
+    Set(rax, num_arguments);
+  }
   LoadAddress(rbx, ExternalReference(f, isolate()));
   CEntryStub ces(isolate(), f->result_size, save_doubles);
   CallStub(&ces);