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

components/subresource_filter/core/common/url_pattern_index.h

Index: components/subresource_filter/core/common/url_pattern_index.h
diff --git a/components/subresource_filter/core/common/url_pattern_index.h b/components/subresource_filter/core/common/url_pattern_index.h
index 30224dce7680cf873b2d8697f285b67abd88ab5d..b08983071fec40dc126eaf530608a5ccd341e516 100644
--- a/components/subresource_filter/core/common/url_pattern_index.h
+++ b/components/subresource_filter/core/common/url_pattern_index.h
@@ -89,6 +89,13 @@ class UrlPatternIndexBuilder {
   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 {
@@ -121,7 +128,8 @@ class UrlPatternIndexMatcher {
                                  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.