sync: Refactor per-datatype throttling

sync/engine/throttled_data_type_tracker.h

Index: sync/engine/throttled_data_type_tracker.h
diff --git a/sync/engine/throttled_data_type_tracker.h b/sync/engine/throttled_data_type_tracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..aa2835bdb696104afa915c4352a2a771ea31afea
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+++ b/sync/engine/throttled_data_type_tracker.h
@@ -0,0 +1,55 @@
+// Copyright (c) 2012 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.
+
+#ifndef SYNC_ENGINE_THROTTLED_DATA_TYPE_TRACKER_H_
+#define SYNC_ENGINE_THROTTLED_DATA_TYPE_TRACKER_H_
+#pragma once
+
+#include <map>
+
+#include "base/gtest_prod_util.h"
+#include "sync/internal_api/public/syncable/model_type.h"
+
+namespace browser_sync {
+
+class AllStatus;
+
+class ThrottledDataTypeTracker {
+ public:
+  // The given allstatus argument will be kept up to date on this object's list
+  // of throttled types.  The argument may be NULL in tests.
+  explicit ThrottledDataTypeTracker(AllStatus* allstatus);
+  ~ThrottledDataTypeTracker();
+
+  // Throttles a set of data types until the specified time is reached.
+  void SetUnthrottleTime(syncable::ModelTypeSet types,
+                         const base::TimeTicks& time);
+
+  // Given an input of the current time (usually from time::Now()), removes from
+  // the set of throttled types any types whose throttling period has expired.
+  void PruneUnthrottledTypes(const base::TimeTicks& time);
+
+  // Returns the set of types which are currently throttled.
+  syncable::ModelTypeSet GetThrottledTypes() const;
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(ThrottledDataTypeTrackerTest,
+                           AddUnthrottleTimeTest);
+  FRIEND_TEST_ALL_PREFIXES(ThrottledDataTypeTrackerTest,
+                           GetCurrentlyThrottledTypesTest);
+
+  typedef std::map<syncable::ModelType, base::TimeTicks> UnthrottleTimes;
+
+  // This is a map from throttled data types to the time at which they can be
+  // unthrottled.
+  UnthrottleTimes unthrottle_times_;
+
+  AllStatus* allstatus_;
+
+  DISALLOW_COPY_AND_ASSIGN(ThrottledDataTypeTracker);
+};
+
+}  // namespace browser_sync
+
+#endif  // SYNC_ENGINE_THROTTLED_DATA_TYPE_TRACKER_H_