[turbofan] Reenable value numbering.

src/compiler/value-numbering-reducer.h

Index: src/compiler/value-numbering-reducer.h
diff --git a/src/compiler/value-numbering-reducer.h b/src/compiler/value-numbering-reducer.h
index 0d67e5dd316ea8faaeca242332a5814693f0f8d4..e0830bbfee6c6d0b04f58e00133c1a87bc336d26 100644
--- a/src/compiler/value-numbering-reducer.h
+++ b/src/compiler/value-numbering-reducer.h
@@ -19,13 +19,14 @@ class ValueNumberingReducer FINAL : public Reducer {
   virtual Reduction Reduce(Node* node) OVERRIDE;
 
  private:
+  enum { kInitialCapacity = 256u, kCapacityToSizeRatio = 2u };
+
+  void Grow();
   Zone* zone() const { return zone_; }
 
-  // TODO(turbofan): We currently use separate chaining with linked lists here,
-  // we may want to replace that with a more sophisticated data structure at
-  // some point in the future.
-  class Entry;
-  Entry* buckets_[117u];
+  Node** entries_;
+  size_t capacity_;
+  size_t size_;
   Zone* zone_;
 };