[BackgroundSync] Add ability to disable Background Sync via Field Trial

content/browser/background_sync/background_sync_manager.cc

Index: content/browser/background_sync/background_sync_manager.cc
diff --git a/content/browser/background_sync/background_sync_manager.cc b/content/browser/background_sync/background_sync_manager.cc
index d56d349051d499eb892dc5462ce1864051b1378b..3589bcc820a68f5fd4bf58d3500bcf3270a114de 100644
--- a/content/browser/background_sync/background_sync_manager.cc
+++ b/content/browser/background_sync/background_sync_manager.cc
@@ -7,6 +7,7 @@
 #include "base/barrier_closure.h"
 #include "base/bind.h"
 #include "base/location.h"
+#include "base/metrics/field_trial.h"
 #include "base/single_thread_task_runner.h"
 #include "base/thread_task_runner_handle.h"
 #include "content/browser/background_sync/background_sync_metrics.h"
@@ -51,6 +52,12 @@ void PostErrorResponse(
           base::Passed(scoped_ptr<BackgroundSyncRegistrationHandle>().Pass())));
 }
 
+bool ShouldDisableForFieldTrial() {
+  std::string experiment = base::FieldTrialList::FindFullName("BackgroundSync");
+  return base::StartsWith(experiment, "ExperimentDisable",
+                          base::CompareCase::INSENSITIVE_ASCII);
+}
+
 }  // namespace
 
 BackgroundSyncManager::BackgroundSyncRegistrations::
@@ -239,6 +246,11 @@ void BackgroundSyncManager::InitImpl(const base::Closure& callback) {
     return;
   }
 
+  if (ShouldDisableForFieldTrial()) {
+    DisableAndClearManager(callback);
+    return;
+  }
+
   GetDataFromBackend(
       kBackgroundSyncUserDataKey,
       base::Bind(&BackgroundSyncManager::InitDidGetDataFromBackend,
@@ -333,6 +345,13 @@ void BackgroundSyncManager::RegisterImpl(
     return;
   }
 
+  if (ShouldDisableForFieldTrial()) {
+    DisableAndClearManager(base::Bind(
+        callback, BACKGROUND_SYNC_STATUS_STORAGE_ERROR,
+        base::Passed(scoped_ptr<BackgroundSyncRegistrationHandle>().Pass())));
+    return;
+  }
+
   if (options.tag.length() > kMaxTagLength) {
     BackgroundSyncMetrics::CountRegister(
         options.periodicity, registration_could_fire,