Compile FastCloneShallowObjectStub using Crankshaft.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index c99240c5b36d76d18caa17909d34d75ab291d9da..e9ff25d5fb764d62cdc771bbca162f5dcb8ba683 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -123,6 +123,7 @@ class LChunkBuilder;
   V(In)                                        \
   V(InstanceOf)                                \
   V(InstanceOfKnownGlobal)                     \
+  V(InstanceSize)                              \
   V(InvokeFunction)                            \
   V(IsConstructCallAndBranch)                  \
   V(IsNilAndBranch)                            \
@@ -3948,6 +3949,26 @@ class HInstanceOfKnownGlobal: public HTemplateInstruction<2> {
 };
 
 
+// TODO(mstarzinger): This instruction should be modeled as a load of the map
+// field followed by a load of the instance size field once HLoadNamedField is
+// flexible enough to accommodate byte-field loads.
+class HInstanceSize: public HTemplateInstruction<1> {
+ public:
+  explicit HInstanceSize(HValue* object) {
+    SetOperandAt(0, object);
+    set_representation(Representation::Integer32());
+  }
+
+  HValue* object() { return OperandAt(0); }
+
+  virtual Representation RequiredInputRepresentation(int index) {
+    return Representation::Tagged();
+  }
+
+  DECLARE_CONCRETE_INSTRUCTION(InstanceSize)
+};
+
+
 class HPower: public HTemplateInstruction<2> {
  public:
   static HInstruction* New(Zone* zone, HValue* left, HValue* right);