Add metrics for quantity and type of Favicon candidates

components/favicon/core/favicon_driver_impl.cc

Index: components/favicon/core/favicon_driver_impl.cc
diff --git a/components/favicon/core/favicon_driver_impl.cc b/components/favicon/core/favicon_driver_impl.cc
index c44b49eda2ddb859d214094821f117e997f08378..453c96b02e0efa5427f298518c969b93a8cb2f21 100644
--- a/components/favicon/core/favicon_driver_impl.cc
+++ b/components/favicon/core/favicon_driver_impl.cc
@@ -5,12 +5,14 @@
 #include "components/favicon/core/favicon_driver_impl.h"
 
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_util.h"
 #include "build/build_config.h"
 #include "components/bookmarks/browser/bookmark_model.h"
 #include "components/favicon/core/favicon_driver_observer.h"
 #include "components/favicon/core/favicon_handler.h"
 #include "components/favicon/core/favicon_service.h"
+#include "components/favicon/core/favicon_url.h"
 #include "components/history/core/browser/history_service.h"
 
 namespace favicon {
@@ -22,6 +24,26 @@ const bool kEnableTouchIcon = true;
 const bool kEnableTouchIcon = false;
 #endif
 
+void RecordCandidateMetrics(const std::vector<FaviconURL>& candidates) {
+  size_t with_defined_touch_icons = 0;
+  size_t with_defined_sizes = 0;
+  for (const auto& candidate : candidates) {
+    if (!candidate.icon_sizes.empty()) {
+      with_defined_sizes++;
+    }
+    if (candidate.icon_type &
+        (favicon_base::IconType::TOUCH_ICON |
+         favicon_base::IconType::TOUCH_PRECOMPOSED_ICON)) {
+      with_defined_touch_icons++;
+    }
+  }
+  UMA_HISTOGRAM_COUNTS_100("Favicons.CandidatesCount", candidates.size());
+  UMA_HISTOGRAM_COUNTS_100("Favicons.CandidatesWithDefinedSizesCount",
+                           with_defined_sizes);
+  UMA_HISTOGRAM_COUNTS_100("Favicons.CandidatesWithTouchIconsCount",
+                           with_defined_touch_icons);
+}
+
 }  // namespace
 
 FaviconDriverImpl::FaviconDriverImpl(FaviconService* favicon_service,
@@ -78,6 +100,7 @@ void FaviconDriverImpl::OnUpdateFaviconURL(
     const GURL& page_url,
     const std::vector<FaviconURL>& candidates) {
   DCHECK(!candidates.empty());
+  RecordCandidateMetrics(candidates);
   favicon_handler_->OnUpdateFaviconURL(page_url, candidates);
   if (touch_icon_handler_.get())
     touch_icon_handler_->OnUpdateFaviconURL(page_url, candidates);