Add NetworkTimeTracker UMA histograms

components/network_time/network_time_tracker.cc

Index: components/network_time/network_time_tracker.cc
diff --git a/components/network_time/network_time_tracker.cc b/components/network_time/network_time_tracker.cc
index dc4ccbb56d3f498294705195257f675a74afbcde..c51937fe700a5933b62a9382274ac58322d4894a 100644
--- a/components/network_time/network_time_tracker.cc
+++ b/components/network_time/network_time_tracker.cc
@@ -13,6 +13,8 @@
 #include "base/json/json_reader.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/metrics/sparse_histogram.h"
 #include "base/rand_util.h"
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
@@ -367,6 +369,9 @@ void NetworkTimeTracker::CheckTime() {
                               net::LOAD_DO_NOT_SAVE_COOKIES |
                               net::LOAD_DO_NOT_SEND_COOKIES |
                               net::LOAD_DO_NOT_SEND_AUTH_DATA);
+
+  UMA_HISTOGRAM_BOOLEAN("NetworkTimeTracker.UpdateTimeFetchAttempted", true);
+
   time_fetcher_->Start();
   fetch_started_ = tick_clock_->NowTicks();
 
@@ -374,40 +379,54 @@ void NetworkTimeTracker::CheckTime() {
 }
 
 bool NetworkTimeTracker::UpdateTimeFromResponse() {
-  if (time_fetcher_->GetStatus().status() != net::URLRequestStatus::SUCCESS &&
+  if (time_fetcher_->GetStatus().status() != net::URLRequestStatus::SUCCESS ||
       time_fetcher_->GetResponseCode() != 200) {
     DVLOG(1) << "fetch failed, status=" << time_fetcher_->GetStatus().status()
              << ",code=" << time_fetcher_->GetResponseCode();
+    // The error code is negated because net errors are negative, but
+    // the corresponding histogram enum is positive.
+    UMA_HISTOGRAM_SPARSE_SLOWLY("NetworkTimeTracker.UpdateTimeFetchFailed",
+                                -time_fetcher_->GetStatus().error());
     return false;
   }
 
+  const char kHistogramName[] = "NetworkTimeTracker.UpdateTimeFetchValid";
+
   std::string response_body;
   if (!time_fetcher_->GetResponseAsString(&response_body)) {
     DVLOG(1) << "failed to get response";
+    UMA_HISTOGRAM_BOOLEAN(kHistogramName, false);

[Steven Holte, 2016/07/28 19:22:46]

This macro uses a static pointer to the underlying Histogram object, so it is
generally prefered to use the histogram name inline, and only invoke the macro
from a single place.  You can coalesce these by using a helper function in the
anonymous namespace.

[estark, 2016/07/28 20:30:49]

Done.

     return false;
   }
   DCHECK(query_signer_);
   if (!query_signer_->ValidateResponse(response_body,
                                        GetServerProof(time_fetcher_.get()))) {
     DVLOG(1) << "invalid signature";
+    UMA_HISTOGRAM_BOOLEAN(kHistogramName, false);
     return false;
   }
   response_body = response_body.substr(5);  // Skips leading )]}'\n
   std::unique_ptr<base::Value> value = base::JSONReader::Read(response_body);
   if (!value) {
     DVLOG(1) << "bad JSON";
+    UMA_HISTOGRAM_BOOLEAN(kHistogramName, false);
     return false;
   }
   const base::DictionaryValue* dict;
   if (!value->GetAsDictionary(&dict)) {
     DVLOG(1) << "not a dictionary";
+    UMA_HISTOGRAM_BOOLEAN(kHistogramName, false);
     return false;
   }
   double current_time_millis;
   if (!dict->GetDouble("current_time_millis", &current_time_millis)) {
     DVLOG(1) << "no current_time_millis";
+    UMA_HISTOGRAM_BOOLEAN(kHistogramName, false);
     return false;
   }
+
+  UMA_HISTOGRAM_BOOLEAN(kHistogramName, true);
+
   // There is a "server_nonce" key here too, but it serves no purpose other than
   // to make the server's response unpredictable.
   base::Time current_time = base::Time::FromJsTime(current_time_millis);