Attempt an on-demand time fetch when encountering a date invalid error

components/network_time/network_time_tracker.cc

Index: components/network_time/network_time_tracker.cc
diff --git a/components/network_time/network_time_tracker.cc b/components/network_time/network_time_tracker.cc
index 2be937662e8e777b846d931adaaa3aa51413a20e..f77b2195323b80b4a03c7de5e9cd29e562349b98 100644
--- a/components/network_time/network_time_tracker.cc
+++ b/components/network_time/network_time_tracker.cc
@@ -100,9 +100,19 @@ const char kVariationsServiceCheckTimeIntervalSeconds[] =
     "CheckTimeIntervalSeconds";
 const char kVariationsServiceRandomQueryProbability[] =
     "RandomQueryProbability";
-// This parameter must have the value "true" in order for
-// StartTimeFetch() to start time queries on demand.
-const char kVariationsServiceEnableFetchesOnDemand[] = "EnableFetchesOnDemand";
+
+// This parameter can have three values:
+//
+// - "background-only": Time queries will be issued in the background as
+//   needed (when the clock loses sync), but on-demand time queries will
+//   not be issued (i.e. StartTimeFetch() will not start time queries.)
+//
+// - "on-demand-only": Time queries will not be issued except when
+//   StartTimeFetch() is called.
+//
+// - "background-and-on-demand": Time queries will be issued both in the
+//   background as needed and also on-demand.
+const char kVariationsServiceFetchBehavior[] = "FetchBehavior";
 
 // This is an ECDSA prime256v1 named-curve key.
 const int kKeyVersion = 1;
@@ -302,6 +312,10 @@ void NetworkTimeTracker::WaitForFetchForTesting(uint32_t nonce) {
   run_loop.Run();
 }
 
+void NetworkTimeTracker::OverrideNonceForTesting(uint32_t nonce) {
+  query_signer_->OverrideNonceForTesting(kKeyVersion, nonce);
+}
+
 base::TimeDelta NetworkTimeTracker::GetTimerDelayForTesting() const {
   DCHECK(timer_.IsRunning());
   return timer_.GetCurrentDelay();
@@ -376,8 +390,8 @@ bool NetworkTimeTracker::StartTimeFetch(const base::Closure& closure) {
   DCHECK(thread_checker_.CalledOnValidThread());
   // Check if the user is opted in to on-demand time fetches.
   const std::string param = variations::GetVariationParamValueByFeature(
-      kNetworkTimeServiceQuerying, kVariationsServiceEnableFetchesOnDemand);
-  if (param != "true") {
+      kNetworkTimeServiceQuerying, kVariationsServiceFetchBehavior);
+  if (param != "on-demand-only" && param != "background-and-on-demand") {
     return false;
   }
 
@@ -536,6 +550,13 @@ void NetworkTimeTracker::OnURLFetchComplete(const net::URLFetcher* source) {
 }
 
 void NetworkTimeTracker::QueueCheckTime(base::TimeDelta delay) {
+  // Check if the user is opted in to background time fetches.
+  const std::string param = variations::GetVariationParamValueByFeature(
+      kNetworkTimeServiceQuerying, kVariationsServiceFetchBehavior);
+  if (param != "background-only" && param != "background-and-on-demand") {
+    return;

[meacer, 2016/11/01 22:20:18]

nit: Maybe revert the condition? It's a bit more readable:

if (param == "on-demand-only" ) {
  timer_.Start(...)
}

[estark, 2016/11/02 19:58:13]

Done.

+  }
+
   timer_.Start(FROM_HERE, delay, this, &NetworkTimeTracker::CheckTime);
 }