Add calculation of derived features for distillable page model

components/dom_distiller/core/page_features.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_DOM_DISTILLER_CORE_PAGE_FEATURES_H_
+#define COMPONENTS_DOM_DISTILLER_CORE_PAGE_FEATURES_H_
+
+#include <vector>
+
+#include "base/values.h"
+#include "url/gurl.h"
+
+namespace dom_distiller {
+
+// The distillable page detector is a model trained on a list of numeric
+// features derived from core more complex features of a webpage (like the
+// body's .textContent). This derives the numeric features for a set of core
+// features.
+//
+// Note: It is crucial that these features are derived in the same way and are
+// in the same order as in the training pipeline. See //heuristics/distillable
+// in the external DomDistillerJs repo.
+std::vector<double> CalculateDerivedFeatures(bool isOGArticle,
+                                             const GURL& url,
+                                             double numElements,
+                                             double numAnchors,
+                                             double numForms,
+                                             const std::string& innerText,
+                                             const std::string& textContent,
+                                             const std::string& innerHTML);
+
+// Calculates the derived features from the JSON value as returned by the
+// javascript core feature extraction.
+std::vector<double> CalculateDerivedFeaturesFromJSON(const base::Value* json);
+
+}  // namespace dom_distiller
+
+#endif  // COMPONENTS_DOM_DISTILLER_CORE_PAGE_FEATURES_H_