Expose API to store and load data usage stats from UI task runner.

components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h b/components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h
index f89df7c29239857ffdff2c1b7ee9a7717b836f80..14e82c1f90695b56e34cd73f5da0972c105500b7 100644
--- a/components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h
+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_test_utils.h
@@ -151,7 +151,7 @@ class MockDataReductionProxyService : public DataReductionProxyService {
       DataReductionProxySettings* settings,
       PrefService* prefs,
       net::URLRequestContextGetter* request_context,
-      scoped_refptr<base::SingleThreadTaskRunner> io_task_runner);
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
   ~MockDataReductionProxyService() override;
 
   MOCK_METHOD2(SetProxyPrefs, void(bool enabled, bool at_startup));
@@ -163,7 +163,7 @@ class MockDataReductionProxyService : public DataReductionProxyService {
 class TestDataReductionProxyIOData : public DataReductionProxyIOData {
  public:
   TestDataReductionProxyIOData(
-      scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
       scoped_ptr<DataReductionProxyConfig> config,
       scoped_ptr<DataReductionProxyEventCreator> event_creator,
       scoped_ptr<DataReductionProxyRequestOptions> request_options,
@@ -286,6 +286,10 @@ class DataReductionProxyTestContext {
   // built with SkipSettingsInitialization.
   void InitSettings();
 
+  // Destroys the |DataReductionProxySettings| object and waits until objects on
+  // the DB task runner are destroyed.
+  void DestroySettings();
+
   // Creates a |DataReductionProxyService| object, or a
   // |MockDataReductionProxyService| if built with
   // WithMockDataReductionProxyService. Can only be called if built with
@@ -410,7 +414,7 @@ class DataReductionProxyTestContext {
   };
 
   DataReductionProxyTestContext(
-      scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
       scoped_ptr<TestingPrefServiceSimple> simple_pref_service,
       scoped_ptr<net::TestNetLog> net_log,
       scoped_refptr<net::URLRequestContextGetter> request_context_getter,