Add metrics for certificate report uploads

chrome/browser/safe_browsing/certificate_reporting_service.h

Index: chrome/browser/safe_browsing/certificate_reporting_service.h
diff --git a/chrome/browser/safe_browsing/certificate_reporting_service.h b/chrome/browser/safe_browsing/certificate_reporting_service.h
index 639b27e34a9372cde43e7d421b50b78601425bae..6aac1a7d029432bb1067108ff0c1369c7a921483 100644
--- a/chrome/browser/safe_browsing/certificate_reporting_service.h
+++ b/chrome/browser/safe_browsing/certificate_reporting_service.h
@@ -55,6 +55,24 @@ class SafeBrowsingService;
 // extended reporting preferences.
 class CertificateReportingService : public KeyedService {
  public:
+  // Events for UMA. Do not rename or remove values, add new values to the end.
+  // Public for testing.
+  enum UMAEvent {

[Jialiu Lin, 2017/05/05 00:25:43]

nit: how about "ReportOutcome"?  "UMAEvent" sounds a little bit too general.

[estark, 2017/05/05 16:21:13]

+1

[meacer, 2017/05/05 19:24:19]

Done.

+    // A report is submitted. This includes failed and successful uploads as
+    // well as uploads that never return a response.
+    REPORT_SUBMITTED,

[estark, 2017/05/05 16:21:13]

Not sure but I think you're supposed to explicitly index (i.e. add " = 0" here)

[meacer, 2017/05/05 19:24:19]

Done.

+    // A report submission failed.
+    REPORT_FAILED,
+    // A report submission was successful.

[estark, 2017/05/05 16:21:13]

nit: perhaps define successful (HTTP 200 status code?)

[meacer, 2017/05/05 19:24:19]

Done.

+    REPORT_SUCCESSFUL,
+    // A report was dropped from the reporting queue because it was older
+    // than report TTL, or it was ignored because the queue was full and the
+    // report was older than the oldest report in the queue. Does not include
+    // reports that were cleared because of a SafeBrowsing preference change.
+    REPORT_DROPPED_OR_IGNORED,
+    REPORT_EVENT_COUNT
+  };
+
   // Represents a report to be sent.
   struct Report {
     int report_id;
@@ -153,6 +171,8 @@ class CertificateReportingService : public KeyedService {
     DISALLOW_COPY_AND_ASSIGN(Reporter);
   };
 
+  static const char kReportEventHistogram[];

[estark, 2017/05/05 16:21:13]

nit: also "Public for testing"

[meacer, 2017/05/05 19:24:19]

Done.

+
   CertificateReportingService(
       safe_browsing::SafeBrowsingService* safe_browsing_service,
       scoped_refptr<net::URLRequestContextGetter> url_request_context_getter,