Revert "Eliminatable CheckMaps replaced with if(true) or if(false)."

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 59341c032a65042feca41112fba2fc9ef7afa460..f9e09c0c7aa146dbc1aa64e605c5220b0169f598 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -707,6 +707,7 @@ void HInstruction::PrintMnemonicTo(StringStream* stream) {
 
 void HInstruction::Unlink() {
   ASSERT(IsLinked());
+  ASSERT(!IsControlInstruction());  // Must never move control instructions.
   ASSERT(!IsBlockEntry());  // Doesn't make sense to delete these.
   ASSERT(previous_ != NULL);
   previous_->next_ = next_;