Add instrumentation hooks to mesaure which subresource filter rules are used.

components/subresource_filter/core/common/url_pattern_index.h

 // Copyright 2017 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_SUBRESOURCE_FILTER_CORE_COMMON_URL_PATTERN_INDEX_H_
 #define COMPONENTS_SUBRESOURCE_FILTER_CORE_COMMON_URL_PATTERN_INDEX_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 71 matching lines @@
 
   // A fallback list that contains all the rules with no acceptable N-gram.
   MutableUrlRuleList fallback_rules_;
 
   // Must outlive this instance.
   flatbuffers::FlatBufferBuilder* flat_builder_;
 
   DISALLOW_COPY_AND_ASSIGN(UrlPatternIndexBuilder);
 };
 
+// Need some way to inject ruleset reporting.
+class RuleRecorder {
+ public:
+  virtual void RecordRuleUsage(const flat::UrlRule* rule) = 0;
+  virtual ~RuleRecorder(){};
+};
+
 // Encapsulates a read-only index built over the URL patterns of a set of URL
 // rules, and provides fast matching of network requests against these rules.
 class UrlPatternIndexMatcher {
  public:
   // Creates an instance to access the given |flat_index|. If |flat_index| is
   // nullptr, then all requests return no match.
   explicit UrlPatternIndexMatcher(const flat::UrlPatternIndex* flat_index);
   ~UrlPatternIndexMatcher();
 
   // If the index contains one or more UrlRules that match the request, returns
@@ skipping 12 matching lines @@
   //  - The |first_party_origin| matches the rule's targeted domains list.
   //  - |element_type| or |activation_type| is among the rule's targeted types.
   //  - The |is_third_party| bit matches the rule's requirement on the requested
   //    |url| being first-/third-party w.r.t. its |first_party_origin|.
   //  - The rule is not generic if |disable_generic_rules| is true.
   const flat::UrlRule* FindMatch(const GURL& url,
                                  const url::Origin& first_party_origin,
                                  proto::ElementType element_type,
                                  proto::ActivationType activation_type,
                                  bool is_third_party,
-                                 bool disable_generic_rules) const;
+                                 bool disable_generic_rules,
+                                 RuleRecorder* recorder) const;
 
  private:
   // Must outlive this instance.
   const flat::UrlPatternIndex* flat_index_;
 
   DISALLOW_COPY_AND_ASSIGN(UrlPatternIndexMatcher);
 };
 
 }  // namespace subresource_filter
 
 #endif  // COMPONENTS_SUBRESOURCE_FILTER_CORE_COMMON_URL_PATTERN_INDEX_H_