[turbofan] First step towards sanitizing for-in and making it optimizable.

src/compiler/control-builders.h

Index: src/compiler/control-builders.h
diff --git a/src/compiler/control-builders.h b/src/compiler/control-builders.h
index c85714ea10877afece48677d09b82284bbcdc994..9f3afce8366efa93413112009305d2abba2504ee 100644
--- a/src/compiler/control-builders.h
+++ b/src/compiler/control-builders.h
@@ -131,6 +131,9 @@ class BlockBuilder final : public ControlBuilder {
   // Primitive support for break.
   void Break() final;
 
+  // Compound control commands for conditional break.
+  void BreakWhen(Node* condition, BranchHint = BranchHint::kNone);
+
  private:
   Environment* break_environment_;  // Environment after the block exits.
 };