Add UMA for the content suggestions settings

chrome/browser/ntp_snippets/ntp_snippets_metrics.h

Index: chrome/browser/ntp_snippets/ntp_snippets_metrics.h
diff --git a/chrome/browser/ntp_snippets/ntp_snippets_metrics.h b/chrome/browser/ntp_snippets/ntp_snippets_metrics.h
index 10c36b818fa31d47820958dfcc6573d87d797398..5687785375e467dfaddba84ac44aa57380a1b137 100644
--- a/chrome/browser/ntp_snippets/ntp_snippets_metrics.h
+++ b/chrome/browser/ntp_snippets/ntp_snippets_metrics.h
@@ -13,6 +13,7 @@ enum ContentSuggestionsNotificationImpression {
 };
 
 // GENERATED_JAVA_ENUM_PACKAGE: org.chromium.chrome.browser.ntp.snippets
+// GENERATED_JAVA_PREFIX_TO_STRIP: CONTENT_SUGGESTIONS_

[Bernhard Bauer, 2017/04/10 23:16:03]

That makes me wonder whether it would make sense to use enum classes here, so
you could remove the prefix already from the C++ enum.

[dgn, 2017/04/10 23:31:29]

Definitely, I was thinking about that. But I'd do it in a separate CL as it
would result in lots of churn on the C++ side. Filed
https://bugs.chromium.org/p/chromium/issues/detail?id=710254

 enum ContentSuggestionsNotificationAction {
   CONTENT_SUGGESTIONS_TAP = 0,    // User tapped notification to open article.
   CONTENT_SUGGESTIONS_DISMISSAL,  // User swiped notification to dismiss it.
@@ -23,9 +24,13 @@ enum ContentSuggestionsNotificationAction {
   CONTENT_SUGGESTIONS_HIDE_DISABLED,   // NTP no longer shows whole category.
   CONTENT_SUGGESTIONS_HIDE_SHUTDOWN,   // Content sugg service is shutting down.
 
+  CONTENT_SUGGESTIONS_OPEN_SETTINGS,  // User opened settings from notification.
+
   MAX_CONTENT_SUGGESTIONS_NOTIFICATION_ACTION
 };
 
+// GENERATED_JAVA_ENUM_PACKAGE: org.chromium.chrome.browser.ntp.snippets
+// GENERATED_JAVA_PREFIX_TO_STRIP: CONTENT_SUGGESTIONS_
 enum ContentSuggestionsNotificationOptOut {
   CONTENT_SUGGESTIONS_IMPLICIT = 0,  // User ignored notifications.
   CONTENT_SUGGESTIONS_EXPLICIT,      // User explicitly opted-out.