Add support for Omaha cohorts to the component updater.

components/update_client/update_checker.cc

Index: components/update_client/update_checker.cc
diff --git a/components/update_client/update_checker.cc b/components/update_client/update_checker.cc
index a5ec2662f4b4e8ba0bf4045c659c1f1f8ba3e7a8..b1815af488eb01808c3ccad934a6dd10e07d4801 100644
--- a/components/update_client/update_checker.cc
+++ b/components/update_client/update_checker.cc
@@ -91,6 +91,15 @@ std::string BuildUpdateCheckRequest(const Configurator& config,
       base::StringAppendF(&app, " %s=\"%s\"", attr.first.c_str(),
                           attr.second.c_str());
     }
+    const std::string& cohort = metadata->GetCohort(item->id);

[Sorin Jianu, 2016/08/18 21:15:15]

This is a small deal and mostly a matter of personal preference. The code is
correct as it is written. However, I avoid references to temporaries and I
prefer to use named local variables in cases like this. The code is as efficient
as the code with references (the temporary is moved into the local variable in
one case, and in the other case the temporary is still created and needs to live
until the end of the scope for the reference).
Why the fuss? Depending what the code does after the call site, I still could
end up with dangling references, so personally, I am always suspicious when I
see the reference to something that is local.

[waffles, 2016/08/18 22:29:23]

Done.

+    const std::string& cohort_name = metadata->GetCohortName(item->id);
+    const std::string& cohort_hint = metadata->GetCohortHint(item->id);
+    if (!cohort.empty())
+      base::StringAppendF(&app, " cohort=\"%s\"", cohort.c_str());
+    if (!cohort_name.empty())
+      base::StringAppendF(&app, " cohortname=\"%s\"", cohort_name.c_str());
+    if (!cohort_hint.empty())
+      base::StringAppendF(&app, " cohorthint=\"%s\"", cohort_hint.c_str());
     base::StringAppendF(&app, ">");
 
     base::StringAppendF(&app, "<updatecheck");
@@ -203,6 +212,14 @@ void UpdateCheckerImpl::OnRequestSenderComplete(
       int daynum = update_response.results().daystart_elapsed_days;
       if (daynum != UpdateResponse::kNoDaystart)
         metadata_->SetDateLastRollCall(*ids_checked, daynum);
+      for (auto result : update_response.results().list) {
+        if (result.set_cohort)
+          metadata_->SetCohort(result.extension_id, result.cohort);
+        if (result.set_cohort_hint)
+          metadata_->SetCohortHint(result.extension_id, result.cohort_hint);
+        if (result.set_cohort_name)
+          metadata_->SetCohortName(result.extension_id, result.cohort_name);
+      }
       base::ThreadTaskRunnerHandle::Get()->PostTask(
           FROM_HERE, base::Bind(update_check_callback_, error,
                                 update_response.results(), retry_after_sec));