[OfflinePages] Adds TimeToStart UMA for background load requests.

components/offline_pages/background/request_coordinator.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/offline_pages/background/request_coordinator.h"
 
 #include <limits>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 56 matching lines @@
     // one to record samples in seconds rather than milliseconds.
     base::HistogramBase* histogram = base::Histogram::FactoryGet(
         AddHistogramSuffix(client_id, "OfflinePages.Background.TimeToSaved"),
         kMinDurationSeconds, kMaxDurationSeconds, kDurationBuckets,
         base::HistogramBase::kUmaTargetedHistogramFlag);
     base::TimeDelta duration = base::Time::Now() - request_creation_time;
     histogram->Add(duration.InSeconds());
   }
 }
 
+void RecordStartTimeUMA(const SavePageRequest& request) {
+  std::string histogram_name("OfflinePages.Background.TimeToStart");
+  if (base::SysInfo::IsLowEndDevice()) {
+    histogram_name += ".Svelte";
+  }
+
+  base::TimeDelta duration = base::Time::Now() - request.creation_time();
+  UMA_HISTOGRAM_CUSTOM_TIMES(

[Steven Holte, 2016/10/20 20:51:11]

Also you shouldn't use this macro with a computed histogram name, since it uses
a static pointer to the histogram.  Instead, use
base::Histogram::FactoryTimeGet() (or split this into seperate macro invokations
for each histogram name)

[dougarnett, 2016/10/21 16:13:48]

Done. Thanks

+      AddHistogramSuffix(request.client_id(), histogram_name.c_str()), duration,
+      base::TimeDelta::FromMilliseconds(100),
+      base::TimeDelta::FromSeconds(kMaxDurationSeconds), kDurationBuckets);

[Steven Holte, 2016/10/20 20:46:31]

You don't want this bound to change even if you change this constant for some
other reason (it will make buckets incompatible between new and old versions of
chrome), so it would be better to just inline the value here.

[dougarnett, 2016/10/21 16:13:48]

Done.

+}
+
 void RecordCancelTimeUMA(const SavePageRequest& canceled_request) {
   // Using regular histogram (with dynamic suffix) rather than time-oriented
   // one to record samples in seconds rather than milliseconds.
   base::HistogramBase* histogram = base::Histogram::FactoryGet(
       AddHistogramSuffix(canceled_request.client_id(),
                          "OfflinePages.Background.TimeToCanceled"),
       kMinDurationSeconds, kMaxDurationSeconds, kDurationBuckets,
       base::HistogramBase::kUmaTargetedHistogramFlag);
   base::TimeDelta duration =
       base::Time::Now() - canceled_request.creation_time();
@@ skipping 453 matching lines @@
   GetOffliner();
   if (!offliner_) {
     DVLOG(0) << "Unable to create Offliner. "
              << "Cannot background offline page.";
     return;
   }
 
   DCHECK(!is_busy_);
   is_busy_ = true;
 
+  // Record start time if this is first attempt.
+  if (request.started_attempt_count() == 0) {
+    RecordStartTimeUMA(request);
+  }
+
   // Mark attempt started in the database and start offliner when completed.
   queue_->MarkAttemptStarted(
       request.request_id(),
       base::Bind(&RequestCoordinator::StartOffliner,
                  weak_ptr_factory_.GetWeakPtr(), request.request_id(),
                  request.client_id().name_space));
 }
 
 void RequestCoordinator::StartOffliner(
     int64_t request_id,
@@ skipping 190 matching lines @@
 
 ClientPolicyController* RequestCoordinator::GetPolicyController() {
   return policy_controller_.get();
 }
 
 void RequestCoordinator::Shutdown() {
   network_quality_estimator_ = nullptr;
 }
 
 }  // namespace offline_pages