Track plugin input event latency

ppapi/api/private/ppb_input_event_private.idl

Index: ppapi/api/private/ppb_input_event_private.idl
diff --git a/ppapi/api/private/ppb_input_event_private.idl b/ppapi/api/private/ppb_input_event_private.idl
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+/* Copyright (c) 2014 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.
+ */
+
+/**
+ * This file defines the PPB_InputEvent_Private interfaces.
+ */
+
+label Chrome {
+  M37 = 0.1
+};
+
+/**
+ * The <code>PPB_InputEvent_Private</code> interface contains pointers to several
+ * functions related to generic input events on the browser.
+ */
+
+interface PPB_InputEvent_Private {
+  /**
+   * TraceInputLatency() traces the latency of the input event. The input
+   * latency is shown in the trace viewer. The starting point of the input
+   * latency is when the input event is sent from renderer to plugin. If the
+   * input event does not cause any rendering damage, the end point of input
+   * latency is when TraceInputLatency() is called on the event. If the input
+   * event does cause rendering damage, the end point of input latency is when
+   * the resulted plugin frame eventually reaches screen.
+   *
+   * Notes: In the current version, only Graphics2D damage is considered as
+   * rendering damage. And it works only when the Graphics2Ds are bound to
+   * the plugin instance.
+   *
+   * @param[in] event A <code>PP_Resource</code> corresponding to an input
+   * event.
+   *
+   * @param[in] has_damage A bool indicating whether the event has caused any
+   * rendering damage.
+   *
+   * @return <code>PP_TRUE</code> if the latency for the given event is tracked.
+   */
+  PP_Bool TraceInputLatency([in] PP_Resource event,
+                            [in] PP_Bool has_damage);
+
+  /**
+   * StartTrackingLatency() requests input latency to be tracked.
+   *
+   * Without calling StartTrackingLatency() first, TraceInputLatency() won't
+   * take effect.
+   *
+   * @param[in] instance The <code>PP_Instance</code> of the instance requesting
+   * to start tracking input latency.
+   */
+  void StartTrackingLatency([in] PP_Instance instance);
+};