[turbofan] Refactor IsSame into NodeProperties.

src/compiler/node-properties.h

Index: src/compiler/node-properties.h
diff --git a/src/compiler/node-properties.h b/src/compiler/node-properties.h
index d428160651294b9155a1f1f677a560a029ce7f41..dd8179f13dfb9108431a6e774202578200b5a5c5 100644
--- a/src/compiler/node-properties.h
+++ b/src/compiler/node-properties.h
@@ -123,6 +123,9 @@ class V8_EXPORT_PRIVATE NodeProperties final {
   //  - Switch: [ IfValue, ..., IfDefault ]
   static void CollectControlProjections(Node* node, Node** proj, size_t count);
 
+  // Checks if two nodes are the same, looking past {CheckHeapObject}.
+  static bool IsSame(Node* a, Node* b);
+
   // ---------------------------------------------------------------------------
   // Context.