Convert WindowOpenDisposition to an enum class.

components/ntp_snippets/content_suggestions_metrics.cc

Index: components/ntp_snippets/content_suggestions_metrics.cc
diff --git a/components/ntp_snippets/content_suggestions_metrics.cc b/components/ntp_snippets/content_suggestions_metrics.cc
index 614ce7567439fd182c10a890d9a95ea5f5401958..5d4fbe169ad5a462da482bcc432b02bbbaa3b785 100644
--- a/components/ntp_snippets/content_suggestions_metrics.cc
+++ b/components/ntp_snippets/content_suggestions_metrics.cc
@@ -181,11 +181,12 @@ void OnSuggestionOpened(int global_position,
 
   LogCategoryHistogramScore(kHistogramOpenedScore, category, score);
 
-  UMA_HISTOGRAM_ENUMERATION(kHistogramOpenDisposition, disposition,
-                            WINDOW_OPEN_DISPOSITION_LAST + 1);
-  LogCategoryHistogramEnumeration(kHistogramOpenDisposition, category,
-                                  disposition,
-                                  WINDOW_OPEN_DISPOSITION_LAST + 1);
+  UMA_HISTOGRAM_ENUMERATION(
+      kHistogramOpenDisposition, static_cast<int>(disposition),
+      static_cast<int>(WindowOpenDisposition::MAX_VALUE) + 1);
+  LogCategoryHistogramEnumeration(
+      kHistogramOpenDisposition, category, static_cast<int>(disposition),
+      static_cast<int>(WindowOpenDisposition::MAX_VALUE) + 1);
 }
 
 void OnSuggestionMenuOpened(int global_position,