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

src/interface-descriptors.cc

Index: src/interface-descriptors.cc
diff --git a/src/interface-descriptors.cc b/src/interface-descriptors.cc
index 89ee9759a9575bd7732eb32346946d23ac535f08..da9eb2991fc8cd7ace2ad255d516500a7a18eb4e 100644
--- a/src/interface-descriptors.cc
+++ b/src/interface-descriptors.cc
@@ -155,6 +155,13 @@ void InstanceofDescriptor::InitializePlatformSpecific(
 }
 
 
+void ToObjectDescriptor::InitializePlatformSpecific(
+    CallInterfaceDescriptorData* data) {
+  Register registers[] = {ReceiverRegister()};
+  data->InitializePlatformSpecific(arraysize(registers), registers);
+}
+
+
 void MathPowTaggedDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {exponent()};