[turbofan] Initial version of branch cloning.

src/compiler/control-flow-optimizer.h

Index: src/compiler/control-flow-optimizer.h
diff --git a/src/compiler/control-flow-optimizer.h b/src/compiler/control-flow-optimizer.h
index fb96e01734e4015e9a4123a0b1cb190bcd136748..d3010217152bbb5f95a0abde7f5416683b21f68d 100644
--- a/src/compiler/control-flow-optimizer.h
+++ b/src/compiler/control-flow-optimizer.h
@@ -31,6 +31,9 @@ class ControlFlowOptimizer FINAL {
   void VisitNode(Node* node);
   void VisitBranch(Node* node);
 
+  bool TryBuildSwitch(Node* node);
+  bool TryCloneBranch(Node* node);
+
   CommonOperatorBuilder* common() const;
   Graph* graph() const;
   JSGraph* jsgraph() const { return jsgraph_; }