[LargeIconService] Report size of the downloaded favicon to UMA

components/favicon/core/large_icon_service.cc

Index: components/favicon/core/large_icon_service.cc
diff --git a/components/favicon/core/large_icon_service.cc b/components/favicon/core/large_icon_service.cc
index e44e5c7d8e189a020004a5bed931b19259677702..616cfd056c7368fd6252e750231178c3f30975a3 100644
--- a/components/favicon/core/large_icon_service.cc
+++ b/components/favicon/core/large_icon_service.cc
@@ -12,6 +12,7 @@
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/stringprintf.h"
 #include "base/task_runner.h"
 #include "base/threading/sequenced_worker_pool.h"
@@ -228,9 +229,13 @@ void OnFetchIconFromGoogleServerComplete(
     favicon_service->UnableToDownloadFavicon(GURL(icon_url));
     base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
                                                   base::Bind(callback, false));
+    UMA_HISTOGRAM_COUNTS_1000("Favicons.LargeIconService.DownloadedSize", 0);
     return;
   }
 
+  UMA_HISTOGRAM_COUNTS_1000("Favicons.LargeIconService.DownloadedSize",
+                            image.Width());

[Ilya Sherman, 2017/04/07 19:26:47]

nit: Histogram macros expand to a fair bit of code, so please help the compiler
be more efficient by providing a small wrapper function for emitting to this
histogram.

[jkrcal, 2017/04/11 19:25:37]

Done.

+
   // TODO(crbug.com/699542): Extract the original icon url from the response
   // headers if available and use it instead of |icon_url|. Possibly the type
   // too, because using TOUCH_ICON is a hacky way that allows us to not