[turbofan] Remove obsolete frame state before comparison.

This removes the obsolete use of FrameStateBeforeAndAfter when visiting
compare operations. None of the operators in question require a "before"
frame state by now.

R=jarin@chromium.org

Review-Url: https://codereview.chromium.org/2144063003
Cr-Commit-Position: refs/heads/master@{#37771}

src/compiler/ast-graph-builder.cc

@@ -2935,11 +2935,10 @@ void AstGraphBuilder::VisitCompareOperation(CompareOperation* expr) {
   }
   VisitForValue(expr->left());
   VisitForValue(expr->right());
-  FrameStateBeforeAndAfter states(this, expr->right()->id());
   Node* right = environment()->Pop();
   Node* left = environment()->Pop();
   Node* value = NewNode(op, left, right);
-  states.AddToNode(value, expr->id(), ast_context()->GetStateCombine());
+  PrepareFrameState(value, expr->id(), ast_context()->GetStateCombine());
   ast_context()->ProduceValue(expr, value);
 }