[stubs] Unify (and optimize) implementation of ToObject.

src/ia32/interface-descriptors-ia32.cc

Index: src/ia32/interface-descriptors-ia32.cc
diff --git a/src/ia32/interface-descriptors-ia32.cc b/src/ia32/interface-descriptors-ia32.cc
index 61508ee596bf44bf49248e3f2fed3530d40561f8..496b34e9ff29095d8d17391eb51c56f3d3100b17 100644
--- a/src/ia32/interface-descriptors-ia32.cc
+++ b/src/ia32/interface-descriptors-ia32.cc
@@ -103,6 +103,10 @@ void ToNumberDescriptor::InitializePlatformSpecific(
 }
 
 
+// static
+const Register ToObjectDescriptor::ReceiverRegister() { return eax; }
+
+
 void NumberToStringDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {eax};