Add data usage tracking for NTP tiles

components/ntp_tiles/popular_sites.cc

Index: components/ntp_tiles/popular_sites.cc
diff --git a/components/ntp_tiles/popular_sites.cc b/components/ntp_tiles/popular_sites.cc
index 912622fae08513f91ef74bca3241af9f29cdd14c..be07d3871f74a8f33e32477586f14aabd0a43034 100644
--- a/components/ntp_tiles/popular_sites.cc
+++ b/components/ntp_tiles/popular_sites.cc
@@ -19,6 +19,7 @@
 #include "base/task_runner_util.h"
 #include "base/time/time.h"
 #include "base/values.h"
+#include "components/data_use_measurement/core/data_use_user_data.h"
 #include "components/google/core/browser/google_util.h"
 #include "components/ntp_tiles/constants.h"
 #include "components/ntp_tiles/pref_names.h"
@@ -278,6 +279,8 @@ void PopularSites::OnReadFileDone(std::unique_ptr<std::string> data,
 
 void PopularSites::FetchPopularSites() {
   fetcher_ = URLFetcher::Create(pending_url_, URLFetcher::GET, this);
+  data_use_measurement::DataUseUserData::AttachToFetcher(
+      fetcher_.get(), data_use_measurement::DataUseUserData::NTP_SNIPPETS);

[sfiera, 2016/08/25 05:39:46]

This doesn't seem like the right enum value. NTP_SNIPPETS is for
components/ntp_snippets, which has a different data usage pattern from here
(steady-state, vs. only new-ish users here).

Popular sites also downloads site icons, so a TODO to count that usage too would
be good. (TODO(sfiera) is fine)

[Raj, 2016/09/22 19:12:03]

Done.

   fetcher_->SetRequestContext(download_context_);
   fetcher_->SetLoadFlags(net::LOAD_DO_NOT_SEND_COOKIES |
                          net::LOAD_DO_NOT_SAVE_COOKIES);