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

src/compiler/control-builders.cc

Index: src/compiler/control-builders.cc
diff --git a/src/compiler/control-builders.cc b/src/compiler/control-builders.cc
index 0e4f1683b86668d5d623f88a56f192cad4bd6ada..6bc364965c0c6a55d7bed600855f9bdad07b2596 100644
--- a/src/compiler/control-builders.cc
+++ b/src/compiler/control-builders.cc
@@ -143,6 +143,16 @@ void BlockBuilder::Break() {
 }
 
 
+void BlockBuilder::BreakWhen(Node* condition, BranchHint hint) {
+  IfBuilder control_if(builder_);
+  control_if.If(condition, hint);
+  control_if.Then();
+  Break();
+  control_if.Else();
+  control_if.End();
+}
+
+
 void BlockBuilder::EndBlock() {
   break_environment_->Merge(environment());
   set_environment(break_environment_);