Rework leaf calls as just simple C calls with a signature and not the NativeArgumentDescriptor.

vm/runtime_entry_ia32.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/runtime_entry.h"
 
 #include "vm/assembler.h"
 #include "vm/stub_code.h"
 
 namespace dart {
 
 #define __ assembler->
 
 
 // Generate code to call into the stub which will call the runtime
 // function. Input for the stub is as follows:
+// For regular runtime calls -
 //   ESP : points to the arguments and return value array.
 //   ECX : address of the runtime function to call.
 //   EDX : number of arguments to the call.
+// For leaf calls the caller is responsible to setup the arguments
+// and look for return values based on the C calling convention.
 void RuntimeEntry::Call(Assembler* assembler) const {
-  __ movl(ECX, Immediate(GetEntryPoint()));
-  __ movl(EDX, Immediate(argument_count()));
-  if (is_leaf()) {
-    __ call(&StubCode::CallToLeafRuntimeLabel());
+  if (!is_leaf()) {
+    __ movl(ECX, Immediate(GetEntryPoint()));
+    __ movl(EDX, Immediate(argument_count()));
+    __ call(&StubCode::CallToRuntimeLabel());
   } else {
-    __ call(&StubCode::CallToRuntimeLabel());
+    ExternalLabel label(name(), GetEntryPoint());
+    __ call(&label);
   }
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32