[runtime] Implement %_ToLength via ToLengthStub.

src/interface-descriptors.h

Index: src/interface-descriptors.h
diff --git a/src/interface-descriptors.h b/src/interface-descriptors.h
index 481ffb9f8f9576a188e8fd182453c8ba10ffc619..42dca2eba727cfb0f3694f77f4172a343ef223d0 100644
--- a/src/interface-descriptors.h
+++ b/src/interface-descriptors.h
@@ -25,6 +25,7 @@ class PlatformInterfaceDescriptor;
   V(FastNewClosure)                           \
   V(FastNewContext)                           \
   V(ToNumber)                                 \
+  V(ToLength)                                 \
   V(ToString)                                 \
   V(ToObject)                                 \
   V(NumberToString)                           \
@@ -373,6 +374,16 @@ class ToNumberDescriptor : public CallInterfaceDescriptor {
 };
 
 
+class ToLengthDescriptor : public CallInterfaceDescriptor {
+ public:
+  enum ParameterIndices { kReceiverIndex };
+
+  DECLARE_DESCRIPTOR(ToLengthDescriptor, CallInterfaceDescriptor)
+
+  static const Register ReceiverRegister();
+};
+
+
 class ToStringDescriptor : public CallInterfaceDescriptor {
  public:
   enum ParameterIndices { kReceiverIndex };