[turbofan] Don't spread global flag checks all over the compiler code.

src/compiler/simplified-lowering.cc

Index: src/compiler/simplified-lowering.cc
diff --git a/src/compiler/simplified-lowering.cc b/src/compiler/simplified-lowering.cc
index 02ddb3d413336545ee0f45e3196f41d9878734d7..d1ab441f5d4d58ae2c57f72190ef3472671cdd88 100644
--- a/src/compiler/simplified-lowering.cc
+++ b/src/compiler/simplified-lowering.cc
@@ -111,13 +111,9 @@ class RepresentationSelector {
       Node* node = *i;
       TRACE(" visit #%d: %s\n", node->id(), node->op()->mnemonic());
       // Reuse {VisitNode()} so the representation rules are in one place.
-      if (FLAG_turbo_source_positions) {
-        SourcePositionTable::Scope scope(
-            source_positions_, source_positions_->GetSourcePosition(node));
-        VisitNode(node, GetUseInfo(node), lowering);
-      } else {
-        VisitNode(node, GetUseInfo(node), lowering);
-      }
+      SourcePositionTable::Scope scope(
+          source_positions_, source_positions_->GetSourcePosition(node));
+      VisitNode(node, GetUseInfo(node), lowering);
     }
 
     // Perform the final replacements.