Implement UMA log throttling for cellular connections

ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc

Index: ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc
diff --git a/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc b/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc
index cb480c2716d2aa9eee7840b8854d79adf9305a8b..7a81bae755b10b3ddb158e63aacd9898f3082758 100644
--- a/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc
+++ b/ios/chrome/browser/metrics/ios_chrome_metrics_service_client.cc
@@ -57,18 +57,18 @@ namespace {
 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
@@ -185,7 +185,9 @@ IOSChromeMetricsServiceClient::CreateUploader(
 }
 
 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);
 }