Implement UMA log throttling for cellular connections

ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc

 // Copyright 2015 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 "ios/chrome/browser/metrics/ios_chrome_metrics_service_client.h"
 
 #include <stdint.h>
 
 #include <utility>
 #include <vector>
@@ skipping 39 matching lines @@
 #include "ios/chrome/browser/ui/browser_otr_state.h"
 #include "ios/chrome/common/channel_info.h"
 #include "ios/web/public/web_thread.h"
 
 namespace {
 
 // Standard interval between log uploads, in seconds.
 const int kStandardUploadIntervalSeconds = 5 * 60;           // Five minutes.
 const int kStandardUploadIntervalCellularSeconds = 15 * 60;  // Fifteen minutes.
 
-// Returns true if current connection type is cellular and user is assigned to
-// experimental group for enabled cellular uploads.
-bool IsCellularLogicEnabled() {
+// Assigns true to output param if current connection type is cellular and user
+// is assigned to experimental group for enabled cellular uploads.

[Alexei Svitkine (slow), 2016/03/31 20:00:40]

What's the reason for this change? Seems like this is only used directly below
and for ProfilerMetricsProvider - neither of which seem like they need the
change. Am I missing something?

Is it because you're not constructing metrics service with the new callback?
Does it really need the version of the callback that has an out param?

[gayane -on leave until 09-2017, 2016/03/31 21:55:10]

I changed this function not to have a return value because I moved it from anon
namespace to be a member function  and had to bind with weakptr. 
But actually I don't remember why I needed it to be a member function.

+void IsCellularLogicEnabled(bool* out_is_enabled) {
   if (variations::GetVariationParamValue("UMA_EnableCellularLogUpload",
                                          "Enabled") != "true" ||
       variations::GetVariationParamValue("UMA_EnableCellularLogUpload",
                                          "Optimize") == "false") {
-    return false;
+    *out_is_enabled = false;
+  } else {
+    *out_is_enabled = net::NetworkChangeNotifier::IsConnectionCellular(
+        net::NetworkChangeNotifier::GetConnectionType());
   }
-
-  return net::NetworkChangeNotifier::IsConnectionCellular(
-      net::NetworkChangeNotifier::GetConnectionType());
 }
 
 }  // namespace
 
 IOSChromeMetricsServiceClient::IOSChromeMetricsServiceClient(
     metrics::MetricsStateManager* state_manager)
     : metrics_state_manager_(state_manager),
       stability_metrics_provider_(nullptr),
       profiler_metrics_provider_(nullptr),
       drive_metrics_provider_(nullptr),
@@ skipping 96 matching lines @@
 IOSChromeMetricsServiceClient::CreateUploader(
     const base::Callback<void(int)>& on_upload_complete) {
   return scoped_ptr<metrics::MetricsLogUploader>(
       new metrics::NetMetricsLogUploader(
           GetApplicationContext()->GetSystemURLRequestContext(),
           metrics::kDefaultMetricsServerUrl, metrics::kDefaultMetricsMimeType,
           on_upload_complete));
 }
 
 base::TimeDelta IOSChromeMetricsServiceClient::GetStandardUploadInterval() {
-  if (IsCellularLogicEnabled())
+  bool is_cellular = false;
+  IsCellularLogicEnabled(&is_cellular);
+  if (is_cellular)
     return base::TimeDelta::FromSeconds(kStandardUploadIntervalCellularSeconds);
   return base::TimeDelta::FromSeconds(kStandardUploadIntervalSeconds);
 }
 
 base::string16 IOSChromeMetricsServiceClient::GetRegistryBackupKey() {
   return base::string16();
 }
 
 void IOSChromeMetricsServiceClient::OnRendererProcessCrash() {
   stability_metrics_provider_->LogRendererCrash();
@@ skipping 128 matching lines @@
                      base::Unretained(this)));
 }
 
 void IOSChromeMetricsServiceClient::OnTabParented(web::WebState* web_state) {
   metrics_service_->OnApplicationNotIdle();
 }
 
 void IOSChromeMetricsServiceClient::OnURLOpenedFromOmnibox(OmniboxLog* log) {
   metrics_service_->OnApplicationNotIdle();
 }