Revert of [Turbofan] Clean up register allocator and verifier code.

src/compiler/register-allocator.h

Index: src/compiler/register-allocator.h
diff --git a/src/compiler/register-allocator.h b/src/compiler/register-allocator.h
index dab26a2a6a3845b4039842d6c9e4036791c9910e..933d1d2472974dc4804582618d050baab6805849 100644
--- a/src/compiler/register-allocator.h
+++ b/src/compiler/register-allocator.h
@@ -999,7 +999,8 @@
   LifetimePosition FindOptimalSpillingPos(LiveRange* range,
                                           LifetimePosition pos);
 
-  const char* RegisterName(MachineRepresentation rep, int code) const;
+  const ZoneVector<TopLevelLiveRange*>& GetFixedRegisters() const;
+  const char* RegisterName(int allocation_index) const;
 
  private:
   RegisterAllocationData* const data_;