Add some initial histograms about subresource filtering.

components/subresource_filter/content/renderer/subresource_filter_agent.cc

Index: components/subresource_filter/content/renderer/subresource_filter_agent.cc
diff --git a/components/subresource_filter/content/renderer/subresource_filter_agent.cc b/components/subresource_filter/content/renderer/subresource_filter_agent.cc
index b7b7ccae80c6b3d2058a53825b16d524d7ab75e5..a7c338db2804f23a6c76e0a32271de5ea0bb1f6d 100644
--- a/components/subresource_filter/content/renderer/subresource_filter_agent.cc
+++ b/components/subresource_filter/content/renderer/subresource_filter_agent.cc
@@ -6,6 +6,7 @@
 
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
+#include "base/metrics/histogram_macros.h"
 #include "components/subresource_filter/content/common/subresource_filter_messages.h"
 #include "components/subresource_filter/content/renderer/document_subresource_filter.h"
 #include "components/subresource_filter/content/renderer/ruleset_dealer.h"
@@ -50,17 +51,44 @@ void SubresourceFilterAgent::ActivateForProvisionalLoad(
   activation_state_for_provisional_load_ = activation_state;
 }
 
+void SubresourceFilterAgent::RecordHistogramsOnLoadCommitted() {
+  UMA_HISTOGRAM_ENUMERATION(
+      "SubresourceFilter.DocumentLoad.ActivationState",
+      static_cast<int>(activation_state_for_provisional_load_),
+      static_cast<int>(ActivationState::LAST) + 1);
+
+  if (activation_state_for_provisional_load_ != ActivationState::DISABLED) {
+    UMA_HISTOGRAM_BOOLEAN("SubresourceFilter.DocumentLoad.RulesetIsAvailable",
+                          !!ruleset_dealer_->ruleset());
+  }
+}
+
+void SubresourceFilterAgent::RecordHistogramsOnLoadFinished() {
+  DCHECK(filter_for_last_committed_load_);
+  UMA_HISTOGRAM_COUNTS_1000(
+      "SubresourceFilter.DocumentLoad.NumSubresourceLoads.Evaluated",
+      filter_for_last_committed_load_->num_loads_evaluated());
+  UMA_HISTOGRAM_COUNTS_1000(
+      "SubresourceFilter.DocumentLoad.NumSubresourceLoads.MatchedRules",
+      filter_for_last_committed_load_->num_loads_matching_rules());
+  UMA_HISTOGRAM_COUNTS_1000(
+      "SubresourceFilter.DocumentLoad.NumSubresourceLoads.Disallowed",
+      filter_for_last_committed_load_->num_loads_disallowed());
+}
+
 void SubresourceFilterAgent::OnDestruct() {
   delete this;
 }
 
 void SubresourceFilterAgent::DidStartProvisionalLoad() {
   activation_state_for_provisional_load_ = ActivationState::DISABLED;
+  filter_for_last_committed_load_.reset();
 }
 
 void SubresourceFilterAgent::DidCommitProvisionalLoad(
     bool is_new_navigation,
     bool is_same_page_navigation) {
+  RecordHistogramsOnLoadCommitted();
   if (activation_state_for_provisional_load_ != ActivationState::DISABLED &&
       ruleset_dealer_->ruleset()) {
     std::vector<GURL> ancestor_document_urls = GetAncestorDocumentURLs();
@@ -68,11 +96,19 @@ void SubresourceFilterAgent::DidCommitProvisionalLoad(
         new DocumentSubresourceFilter(activation_state_for_provisional_load_,
                                       ruleset_dealer_->ruleset(),
                                       std::move(ancestor_document_urls)));
+    filter_for_last_committed_load_ = filter->AsWeakPtr();
     SetSubresourceFilterForCommittedLoad(std::move(filter));
   }
   activation_state_for_provisional_load_ = ActivationState::DISABLED;
 }
 
+void SubresourceFilterAgent::DidFinishLoad() {
+  if (!filter_for_last_committed_load_)
+    return;
+
+  RecordHistogramsOnLoadFinished();
+}
+
 bool SubresourceFilterAgent::OnMessageReceived(const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(SubresourceFilterAgent, message)