Add attempt count metric to FaviconHandler

components/favicon/core/favicon_handler.cc

Index: components/favicon/core/favicon_handler.cc
diff --git a/components/favicon/core/favicon_handler.cc b/components/favicon/core/favicon_handler.cc
index 64c8961ae23ad760d06e826ee6e04bf06b7f1b2d..79f35f0622513060931374b18488cf052049e147 100644
--- a/components/favicon/core/favicon_handler.cc
+++ b/components/favicon/core/favicon_handler.cc
@@ -12,6 +12,7 @@
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/memory/ref_counted_memory.h"
+#include "base/metrics/histogram_macros.h"
 #include "build/build_config.h"
 #include "components/favicon/core/favicon_service.h"
 #include "components/favicon_base/favicon_util.h"
@@ -59,6 +60,25 @@ bool IsValid(const favicon_base::FaviconRawBitmapResult& bitmap_result) {
   return bitmap_result.is_valid();
 }
 
+void RecordAttemptsForHandlerType(

[pkotwicz, 2017/04/12 02:48:20]

Maybe rename this method to: RecordDownloadAttemptsForHandlerType()

[fhorschig, 2017/04/12 08:32:39]

Done.

+    FaviconDriverObserver::NotificationIconType handler_type,
+    int attempts) {
+  switch (handler_type) {
+    case FaviconDriverObserver::NON_TOUCH_16_DIP:
+      UMA_HISTOGRAM_COUNTS_100("Favicons.DownloadAttempts.Favicons", attempts);
+      return;
+    case FaviconDriverObserver::NON_TOUCH_LARGEST:
+      UMA_HISTOGRAM_COUNTS_100("Favicons.DownloadAttempts.LargeIcons",
+                               attempts);
+      return;
+    case FaviconDriverObserver::TOUCH_LARGEST:
+      UMA_HISTOGRAM_COUNTS_100("Favicons.DownloadAttempts.TouchIcons",
+                               attempts);
+      return;
+  }
+  NOTREACHED();
+}
+
 // Returns true if |bitmap_results| is non-empty and:
 // - At least one of the bitmaps in |bitmap_results| is expired
 // OR
@@ -167,6 +187,7 @@ FaviconHandler::FaviconHandler(
       notification_icon_type_(favicon_base::INVALID_ICON),
       service_(service),
       delegate_(delegate),
+      num_download_requests_(0),
       current_candidate_index_(0u) {
   DCHECK(delegate_);
 }
@@ -199,6 +220,7 @@ void FaviconHandler::FetchFavicon(const GURL& url) {
   candidates_.clear();
   notification_icon_url_ = GURL();
   notification_icon_type_ = favicon_base::INVALID_ICON;
+  num_download_requests_ = 0;
   current_candidate_index_ = 0u;
   best_favicon_ = DownloadedFavicon();
 
@@ -311,6 +333,7 @@ void FaviconHandler::OnUpdateFaviconURL(
 
   download_request_.Cancel();
   candidates_ = std::move(sorted_candidates);
+  num_download_requests_ = 0;
   current_candidate_index_ = 0u;
   best_favicon_ = DownloadedFavicon();
 
@@ -399,6 +422,9 @@ void FaviconHandler::OnDidDownloadFavicon(
     ++current_candidate_index_;
     DownloadCurrentCandidateOrAskFaviconService();
   } else {
+    // OnDidDownloadFavicon can only be called after invoking a request, so
+    // |num_download_requests_| can never be 0.

[pkotwicz, 2017/04/12 02:48:21]

Nit: OnDidDownloadFavicon -> OnDidDownloadFavicon()

"invoking a request" -> "requesting a download"

[fhorschig, 2017/04/12 08:32:39]

Done.

+    RecordAttemptsForHandlerType(handler_type_, num_download_requests_);
     // We have either found the ideal candidate or run out of candidates.
     if (best_favicon_.candidate.icon_type != favicon_base::INVALID_ICON) {
       // No more icons to request, set the favicon from the candidate.
@@ -407,6 +433,7 @@ void FaviconHandler::OnDidDownloadFavicon(
     }
     // Clear download related state.
     current_candidate_index_ = candidates_.size();
+    num_download_requests_ = 0;
     best_favicon_ = DownloadedFavicon();
   }
 }
@@ -499,6 +526,9 @@ void FaviconHandler::OnFaviconData(const std::vector<
                                                         favicon_bitmap_results);
 
   if (has_valid_result) {
+    if (num_download_requests_ > 0) {
+      RecordAttemptsForHandlerType(handler_type_, current_candidate_index_);

[pkotwicz, 2017/04/12 02:48:21]

Don't you want to pass |num_download_requests_| here?

You should record this in the else{} statement of
if(has_expired_or_incomplete_result){}
If the icon is expired the current code records the UMA metric twice

[fhorschig, 2017/04/12 08:32:39]

Yes, done.
Done. (It hasn't happened yet because num_download_requests_ was usually 0 at
this
point. There is a test verifying that now.)

+    }
     // There is a valid favicon. Notify any observers. It is useful to notify
     // the observers even if the favicon is expired or incomplete (incorrect
     // size) because temporarily showing the user an expired favicon or
@@ -531,6 +561,7 @@ void FaviconHandler::ScheduleDownload(const GURL& image_url,
                          std::vector<gfx::Size>());
     return;
   }
+  ++num_download_requests_;
   download_request_.Reset(base::Bind(&FaviconHandler::OnDidDownloadFavicon,
                                      base::Unretained(this), icon_type));
   // A max bitmap size is specified to avoid receiving huge bitmaps in