[Icon cacher] Add metrics for downloading favicons for NTP Tiles

components/ntp_tiles/icon_cacher_impl.cc

Index: components/ntp_tiles/icon_cacher_impl.cc
diff --git a/components/ntp_tiles/icon_cacher_impl.cc b/components/ntp_tiles/icon_cacher_impl.cc
index 488e102ff953f4fa9a183f9c4b5c8941a1261799..974e96c06be6ea25fffb7b8aafe24f800066e5a0 100644
--- a/components/ntp_tiles/icon_cacher_impl.cc
+++ b/components/ntp_tiles/icon_cacher_impl.cc
@@ -7,6 +7,7 @@
 #include <utility>
 
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "components/favicon/core/favicon_service.h"
 #include "components/favicon/core/favicon_util.h"
 #include "components/favicon/core/large_icon_service.h"
@@ -32,6 +33,21 @@ constexpr int kDesiredFrameSize = 128;
 constexpr int kTileIconMinSizePx = 48;
 constexpr int kTileIconDesiredSizePx = 96;
 
+// Enumeration listing all possible outcomes for fetch attempts of favicons for
+// NTP tiles. Used for UMA histograms, so do not change existing
+// values. Insert new values at the end, and update the histogram definition.
+enum class TileFaviconFetchResult { SUCCESS = 0, FAILURE = 1, COUNT = 2 };
+
+void RecordPopularSitesFaviconFetchResult(TileFaviconFetchResult result) {
+  UMA_HISTOGRAM_ENUMERATION("NewTabPage.TileFaviconFetched.popular", result,
+                            TileFaviconFetchResult::COUNT);
+}
+
+void RecordMostLikelyFaviconFetchResult(TileFaviconFetchResult result) {
+  UMA_HISTOGRAM_ENUMERATION("NewTabPage.TileFaviconFetched.server", result,
+                            TileFaviconFetchResult::COUNT);
+}
+
 favicon_base::IconType IconType(const PopularSites::Site& site) {
   return site.large_icon_url.is_valid() ? favicon_base::TOUCH_ICON
                                         : favicon_base::FAVICON;
@@ -115,6 +131,7 @@ void IconCacherImpl::OnPopularSitesFaviconDownloaded(
     const image_fetcher::RequestMetadata& metadata) {
   if (fetched_image.IsEmpty()) {
     FinishRequestAndNotifyIconAvailable(site.url, /*newly_available=*/false);
+    RecordPopularSitesFaviconFetchResult(TileFaviconFetchResult::FAILURE);
     return;
   }
 
@@ -125,6 +142,7 @@ void IconCacherImpl::OnPopularSitesFaviconDownloaded(
   }
   SaveIconForSite(site, fetched_image);
   FinishRequestAndNotifyIconAvailable(site.url, /*newly_available=*/true);
+  RecordPopularSitesFaviconFetchResult(TileFaviconFetchResult::SUCCESS);
 }
 
 void IconCacherImpl::SaveAndNotifyDefaultIconForSite(
@@ -196,10 +214,17 @@ void IconCacherImpl::OnGetLargeIconOrFallbackStyleFinished(
   large_icon_service_
       ->GetLargeIconOrFallbackStyleFromGoogleServerSkippingLocalCache(
           page_url, kTileIconMinSizePx, kTileIconDesiredSizePx,
-          base::Bind(&IconCacherImpl::FinishRequestAndNotifyIconAvailable,
+          base::Bind(&IconCacherImpl::OnMostLikelyFaviconDownloaded,
                      weak_ptr_factory_.GetWeakPtr(), page_url));
 }
 
+void IconCacherImpl::OnMostLikelyFaviconDownloaded(const GURL& request_url,
+                                                   bool success) {
+  RecordMostLikelyFaviconFetchResult(success ? TileFaviconFetchResult::SUCCESS
+                                             : TileFaviconFetchResult::FAILURE);
+  FinishRequestAndNotifyIconAvailable(request_url, success);
+}
+
 bool IconCacherImpl::StartRequest(const GURL& request_url,
                                   const base::Closure& icon_available) {
   bool in_flight = in_flight_requests_.count(request_url) > 0;