Compile FastCloneShallowObjectStub using Crankshaft.

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index 061a305354e4aafe4107a3a39dca8651692759a0..0744ed5bf2fcc53224d5088498b66b77cd05915b 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -109,6 +109,7 @@ class LCodeGen;
   V(In)                                         \
   V(InstanceOf)                                 \
   V(InstanceOfKnownGlobal)                      \
+  V(InstanceSize)                               \
   V(InstructionGap)                             \
   V(Integer32ToDouble)                          \
   V(Uint32ToDouble)                             \
@@ -954,6 +955,19 @@ class LInstanceOfKnownGlobal: public LTemplateInstruction<1, 1, 1> {
 };
 
 
+class LInstanceSize: public LTemplateInstruction<1, 1, 0> {
+ public:
+  explicit LInstanceSize(LOperand* object) {
+    inputs_[0] = object;
+  }
+
+  LOperand* object() { return inputs_[0]; }
+
+  DECLARE_CONCRETE_INSTRUCTION(InstanceSize, "instance-size")
+  DECLARE_HYDROGEN_ACCESSOR(InstanceSize)
+};
+
+
 class LBoundsCheck: public LTemplateInstruction<0, 2, 0> {
  public:
   LBoundsCheck(LOperand* index, LOperand* length) {