[crankshaft] Support ES6 tail call elimination.

src/crankshaft/x64/lithium-codegen-x64.h

Index: src/crankshaft/x64/lithium-codegen-x64.h
diff --git a/src/crankshaft/x64/lithium-codegen-x64.h b/src/crankshaft/x64/lithium-codegen-x64.h
index 873a3dd1acc51be9df77178fdd9c9b823309927c..139645e6cdf806bf1dbc6f691f615d0088224cb7 100644
--- a/src/crankshaft/x64/lithium-codegen-x64.h
+++ b/src/crankshaft/x64/lithium-codegen-x64.h
@@ -192,11 +192,14 @@ class LCodeGen: public LCodeGenBase {
 
   void LoadContextFromDeferred(LOperand* context);
 
+  void PrepareForTailCall(const ParameterCount& actual, Register scratch1,
+                          Register scratch2, Register scratch3);
+
   // Generate a direct call to a known function.  Expects the function
   // to be in rdi.
   void CallKnownFunction(Handle<JSFunction> function,
                          int formal_parameter_count, int arity,
-                         LInstruction* instr);
+                         bool is_tail_call, LInstruction* instr);
 
   void RecordSafepointWithLazyDeopt(LInstruction* instr,
                                     SafepointMode safepoint_mode,