Expose a method in VariationsService to trigger a seed fetch.

chrome/browser/metrics/variations/variations_request_scheduler_mobile.cc

 // Copyright (c) 2013 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 "chrome/browser/metrics/variations/variations_request_scheduler_mobile.h"
 
 #include "base/prefs/pref_service.h"
 #include "chrome/common/pref_names.h"
 
 namespace chrome_variations {
 
 namespace {
 
+// Time before attempting a seed fetch after a ScheduleFetch(), in seconds.
+const int kScheduleFetchDelaySeconds = 5;
+
 // Time between seed fetches, in hours.
 const int kSeedFetchPeriodHours = 5;
 
 }  // namespace
 
 VariationsRequestSchedulerMobile::VariationsRequestSchedulerMobile(
     const base::Closure& task,
     PrefService* local_state) :
   VariationsRequestScheduler(task), local_state_(local_state) {
 }
 
 VariationsRequestSchedulerMobile::~VariationsRequestSchedulerMobile() {
 }
 
 void VariationsRequestSchedulerMobile::Start() {
   // Check the time of the last request. If it has been longer than the fetch
   // period, run the task. Otherwise, do nothing. Note that no future requests
   // are scheduled since it is unlikely that the mobile process would live long
   // enough for the timer to fire.
   const base::Time last_fetch_time = base::Time::FromInternalValue(
       local_state_->GetInt64(prefs::kVariationsLastFetchTime));
   if (base::Time::Now() >
       last_fetch_time + base::TimeDelta::FromHours(kSeedFetchPeriodHours)) {
+    last_request_time_ = base::Time::Now();
     task().Run();
   }
 }
 
 void VariationsRequestSchedulerMobile::Reset() {
 }
 
+void VariationsRequestSchedulerMobile::OnAppEnterForeground() {
+  // Verify we haven't just attempted a fetch (which has not completed). This
+  // is mainly used to verify we don't trigger a second fetch for the
+  // OnAppEnterForeground right after startup.
+  if (base::Time::Now() <
+      last_request_time_ + base::TimeDelta::FromHours(kSeedFetchPeriodHours)) {
+    return;
+  }
+
+  // Since Start() launches a one-off execution, we can reuse it here. Also
+  // note that since Start() verifies that the seed needs to be refreshed, we
+  // do not verify here.
+  schedule_fetch_timer_.Start(
+      FROM_HERE,
+      base::TimeDelta::FromSeconds(kScheduleFetchDelaySeconds),
+      this,
+      &VariationsRequestSchedulerMobile::Start);
+}
+
 // static
 VariationsRequestScheduler* VariationsRequestScheduler::Create(
     const base::Closure& task,
     PrefService* local_state) {
   return new VariationsRequestSchedulerMobile(task, local_state);
 }
 
 }  // namespace chrome_variations