Revert of [crankshaft] Fixing ES6 tail call elimination.

src/crankshaft/lithium.h

Index: src/crankshaft/lithium.h
diff --git a/src/crankshaft/lithium.h b/src/crankshaft/lithium.h
index 38e395ea16a34914a0f669bad07a2c89ecdb6cc3..d078611d94ac991c6abae64815a6845af05969a1 100644
--- a/src/crankshaft/lithium.h
+++ b/src/crankshaft/lithium.h
@@ -745,11 +745,6 @@
   // Will not be moved to a register even if one is freely available.
   virtual MUST_USE_RESULT LOperand* UseAny(HValue* value) = 0;
 
-  // Assigns given environment to an instruction.  An instruction which can
-  // deoptimize must have an environment.
-  LInstruction* AssignEnvironment(LInstruction* instr,
-                                  HEnvironment* hydrogen_env);
-
   LEnvironment* CreateEnvironment(HEnvironment* hydrogen_env,
                                   int* argument_index_accumulator,
                                   ZoneList<HValue*>* objects_to_materialize);