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

components/subresource_filter/content/renderer/web_document_subresource_filter_impl.cc

Index: components/subresource_filter/content/renderer/web_document_subresource_filter_impl.cc
diff --git a/components/subresource_filter/content/renderer/web_document_subresource_filter_impl.cc b/components/subresource_filter/content/renderer/web_document_subresource_filter_impl.cc
index de17ed654bc9312e1cb3367380da8cab033cc6b1..9e2560d35d9b9ede17b87cad2920857064e45425 100644
--- a/components/subresource_filter/content/renderer/web_document_subresource_filter_impl.cc
+++ b/components/subresource_filter/content/renderer/web_document_subresource_filter_impl.cc
@@ -6,9 +6,11 @@
 
 #include <utility>
 
+#include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "components/subresource_filter/core/common/activation_state.h"
 #include "components/subresource_filter/core/common/memory_mapped_ruleset.h"
+#include "components/subresource_filter/core/common/url_pattern.h"
 #include "third_party/WebKit/public/platform/WebURL.h"
 #include "third_party/WebKit/public/platform/WebURLRequest.h"
 #include "url/gurl.h"
@@ -87,6 +89,39 @@ WebLoadPolicy ToWebLoadPolicy(LoadPolicy load_policy) {
   }
 }
 
+class LogRuleRecorder : public RuleRecorder {
+ public:
+  ~LogRuleRecorder() override {}
+  void RecordRuleUsage(const flat::UrlRule* rule) override {
+    if (!rule)
+      return;
+    std::string domains;
+    auto* domains_included = rule->domains_included();
+    auto* domains_excluded = rule->domains_excluded();
+    if (domains_included || domains_excluded) {
+      domains += " Domains:";
+      if (domains_included) {
+        domains += " +(";
+        for (const auto* domain : *domains_included) {
+          domains += domain->str();
+          domains += " ";
+        }
+        domains += ")";
+      }
+      if (domains_excluded) {
+        domains += " -(";
+        for (const auto* domain : *domains_excluded) {
+          domains += domain->str();
+          domains += " ";
+        }
+        domains += ")";
+      }
+    }
+    UrlPattern pattern(*rule);
+    LOG(ERROR) << "rule " << pattern << domains;
+  }
+};
+
 }  // namespace
 
 WebDocumentSubresourceFilterImpl::~WebDocumentSubresourceFilterImpl() = default;
@@ -96,7 +131,10 @@ WebDocumentSubresourceFilterImpl::WebDocumentSubresourceFilterImpl(
     ActivationState activation_state,
     scoped_refptr<const MemoryMappedRuleset> ruleset,
     base::OnceClosure first_disallowed_load_callback)
-    : filter_(std::move(document_origin), activation_state, std::move(ruleset)),
+    : filter_(std::move(document_origin),
+              activation_state,
+              std::move(ruleset),
+              base::MakeUnique<LogRuleRecorder>()),
       first_disallowed_load_callback_(
           std::move(first_disallowed_load_callback)) {}