Revert of [crankshaft] Fixing ES6 tail call elimination.

src/crankshaft/mips64/lithium-mips64.h

Index: src/crankshaft/mips64/lithium-mips64.h
diff --git a/src/crankshaft/mips64/lithium-mips64.h b/src/crankshaft/mips64/lithium-mips64.h
index dc0990b5810052042d0b9a491831b79f6ae50528..931682d26adac033b771ff09e6200ee6963a5623 100644
--- a/src/crankshaft/mips64/lithium-mips64.h
+++ b/src/crankshaft/mips64/lithium-mips64.h
@@ -224,11 +224,6 @@
   void MarkAsCall() { bit_field_ = IsCallBits::update(bit_field_, true); }
   bool IsCall() const { return IsCallBits::decode(bit_field_); }
 
-  void MarkAsTailCall() {
-    bit_field_ = IsTailCallBits::update(bit_field_, true);
-  }
-  bool IsTailCall() const { return IsTailCallBits::decode(bit_field_); }
-
   // Interface to the register allocator and iterators.
   bool ClobbersTemps() const { return IsCall(); }
   bool ClobbersRegisters() const { return IsCall(); }
@@ -263,7 +258,6 @@
   virtual LOperand* TempAt(int i) = 0;
 
   class IsCallBits: public BitField<bool, 0, 1> {};
-  class IsTailCallBits : public BitField<bool, IsCallBits::kNext, 1> {};
 
   LEnvironment* environment_;
   SetOncePointer<LPointerMap> pointer_map_;