Revert of [crankshaft] Fixing ES6 tail call elimination.

src/crankshaft/mips/lithium-mips.h

Index: src/crankshaft/mips/lithium-mips.h
diff --git a/src/crankshaft/mips/lithium-mips.h b/src/crankshaft/mips/lithium-mips.h
index cc09d5ce2ace5fecb11a71417e7f3eb1b1d4078a..a8279a9a27b2252db3ffb60aecd608f9585de00c 100644
--- a/src/crankshaft/mips/lithium-mips.h
+++ b/src/crankshaft/mips/lithium-mips.h
@@ -221,11 +221,6 @@
   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(); }
@@ -260,7 +255,6 @@
   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_;