Add monomorphic CompareNilICs and Crankshaft support

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 2fecc1e44c9180b88bb4039b3c5b5196123878af..d447fab0a1bdeabd7bc5e37060a641c73cf3d8b2 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -134,6 +134,19 @@ void ArrayNArgumentsConstructorStub::InitializeInterfaceDescriptor(
 }
 
 
+void CompareNilICStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  static Register registers[] = { rax };
+  descriptor->register_param_count_ = 1;
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ =
+      FUNCTION_ADDR(CompareNilIC_Miss);
+  descriptor->miss_handler_ =
+      ExternalReference(IC_Utility(IC::kCompareNilIC_Miss), isolate);
+}
+
+
 #define __ ACCESS_MASM(masm)