[turbofan] removed some dead code.

src/compiler/register-allocator.cc

Index: src/compiler/register-allocator.cc
diff --git a/src/compiler/register-allocator.cc b/src/compiler/register-allocator.cc
index 05bc8ba795c1b46fd59b35f1463b5b999fbb12c0..d06ed0243ee25e9f5cda8801190f3d6f2634e096 100644
--- a/src/compiler/register-allocator.cc
+++ b/src/compiler/register-allocator.cc
@@ -435,9 +435,6 @@ LiveRange* LiveRange::SplitAt(LifetimePosition position, Zone* zone) {
   child->top_level_ = TopLevel();
   child->next_ = next_;
   next_ = child;
-  if (child->next() == nullptr) {
-    TopLevel()->set_last_child(child);
-  }
   return child;
 }
 
@@ -534,15 +531,6 @@ UsePosition* LiveRange::DetachAt(LifetimePosition position, LiveRange* result,
 }
 
 
-void LiveRange::AppendAsChild(TopLevelLiveRange* other) {
-  next_ = other;
-
-  other->UpdateParentForAllChildren(TopLevel());
-  TopLevel()->UpdateSpillRangePostMerge(other);
-  TopLevel()->set_last_child(other->last_child());
-}
-
-
 void LiveRange::UpdateParentForAllChildren(TopLevelLiveRange* new_top_level) {
   LiveRange* child = this;
   for (; child != nullptr; child = child->next()) {
@@ -683,7 +671,6 @@ TopLevelLiveRange::TopLevelLiveRange(int vreg, MachineRepresentation rep)
       spill_move_insertion_locations_(nullptr),
       spilled_in_deferred_blocks_(false),
       spill_start_index_(kMaxInt),
-      last_child_(this),
       last_pos_(nullptr),
       splinter_(nullptr),
       has_preassigned_slot_(false) {