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diff --git a/gfx/layers/apz/src/PotentialCheckerboardDurationTracker.h b/gfx/layers/apz/src/PotentialCheckerboardDurationTracker.h
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+++ b/gfx/layers/apz/src/PotentialCheckerboardDurationTracker.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layers_PotentialCheckerboardDurationTracker_h
+#define mozilla_layers_PotentialCheckerboardDurationTracker_h
+
+#include "mozilla/TimeStamp.h"
+
+namespace mozilla {
+namespace layers {
+
+/**
+ * This class allows the owner to track the duration of time considered
+ * "potentially checkerboarding". This is the union of two possibly-intersecting
+ * sets of time periods. The first set is that in which checkerboarding was
+ * actually happening, since by definition it could potentially be happening.
+ * The second set is that in which the APZC is actively transforming content
+ * in the compositor, since it could potentially transform it so as to display
+ * checkerboarding to the user.
+ * The caller of this class calls the appropriate methods to indicate the start
+ * and stop of these two sets, and this class manages accumulating the union
+ * of the various durations.
+ */
+class PotentialCheckerboardDurationTracker {
+public:
+  PotentialCheckerboardDurationTracker();
+
+  /**
+   * This should be called if checkerboarding is encountered. It can be called
+   * multiple times during a checkerboard event.
+   */
+  void CheckerboardSeen();
+  /**
+   * This should be called when checkerboarding is done. It must have been
+   * preceded by one or more calls to CheckerboardSeen().
+   */
+  void CheckerboardDone();
+
+  /**
+   * This should be called at composition time, to indicate if the APZC is in
+   * a transforming state or not.
+   */
+  void InTransform(bool aInTransform);
+
+private:
+  bool Tracking() const;
+
+private:
+  bool mInCheckerboard;
+  bool mInTransform;
+
+  TimeStamp mCurrentPeriodStart;
+};
+
+} // namespace layers
+} // namespace mozilla
+
+#endif // mozilla_layers_PotentialCheckerboardDurationTracker_h