[turbofan] Add support for copy-on-write element stores.

src/interface-descriptors.h

Index: src/interface-descriptors.h
diff --git a/src/interface-descriptors.h b/src/interface-descriptors.h
index 430090c2473e5a41acc72bae2014da579e14c9cc..1460b3c86562d86c87c25362f34585d60057fce4 100644
--- a/src/interface-descriptors.h
+++ b/src/interface-descriptors.h
@@ -55,6 +55,7 @@ class PlatformInterfaceDescriptor;
   V(ConstructStub)                     \
   V(ConstructTrampoline)               \
   V(RegExpConstructResult)             \
+  V(CopyFixedArray)                    \
   V(TransitionElementsKind)            \
   V(AllocateHeapNumber)                \
   V(AllocateFloat32x4)                 \
@@ -648,6 +649,12 @@ class StoreGlobalViaContextDescriptor : public CallInterfaceDescriptor {
   static const Register ValueRegister();
 };
 
+class CopyFixedArrayDescriptor : public CallInterfaceDescriptor {
+ public:
+  DEFINE_PARAMETERS(kSource)
+  DECLARE_DEFAULT_DESCRIPTOR(CopyFixedArrayDescriptor, CallInterfaceDescriptor,
+                             kParameterCount)
+};
 
 class TransitionElementsKindDescriptor : public CallInterfaceDescriptor {
  public: