Factor out latency tracking from RenderWidgetHostImpl

content/browser/renderer_host/render_widget_host_latency_tracker.h

Index: content/browser/renderer_host/render_widget_host_latency_tracker.h
diff --git a/content/browser/renderer_host/render_widget_host_latency_tracker.h b/content/browser/renderer_host/render_widget_host_latency_tracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..0d7391b7a80dbdf583af8a09a4096d0388fed206
--- /dev/null
+++ b/content/browser/renderer_host/render_widget_host_latency_tracker.h
@@ -0,0 +1,70 @@
+// Copyright 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.
+
+#ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_LATENCY_TRACKER_H_
+#define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_LATENCY_TRACKER_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "content/browser/renderer_host/event_with_latency_info.h"
+#include "ui/events/latency_info.h"
+
+namespace content {
+
+// Utility class for tracking the latency of events passing through
+// a given RenderWidgetHost.
+class RenderWidgetHostLatencyTracker {
+ public:
+  RenderWidgetHostLatencyTracker();
+  ~RenderWidgetHostLatencyTracker();
+
+  // Associates the latency tracker with a given route and process.
+  // Called once after the RenderWidgetHost is fully initialized.
+  void Initialize(int routing_id, int process_id);
+
+  // Populates the LatencyInfo with relevant entries for latency tracking.
+  // Called when an event is received by the RenderWidgetHost, prior to
+  // that event being forwarded to the renderer (via the InputRouter).
+  void OnInputEvent(const blink::WebInputEvent& event,
+                    ui::LatencyInfo* latency);
+
+  // Populates the LatencyInfo with relevant entries for latency tracking, also
+  // terminating latency tracking for events that did not trigger rendering and
+  // performing relevant UMA latency reporting. Called when an event is ack'ed
+  // to the RenderWidgetHost (from the InputRouter).
+  void OnInputEventAck(const blink::WebInputEvent& event,
+                       ui::LatencyInfo* latency);
+
+  // Populates renderer-created LatencyInfo entries with the appropriate latency
+  // component id. Called when the RenderWidgetHost receives a compositor swap
+  // update from the renderer.
+  void OnSwapCompositorFrame(std::vector<ui::LatencyInfo>* latencies);
+
+  // Terminates latency tracking for events that triggered rendering, also
+  // performing relevant UMA latency reporting.
+  // Called when the RenderWidgetHost receives a swap update from the GPU.
+  void OnFrameSwapped(const ui::LatencyInfo& latency);
+
+  // WebInputEvent coordinates are in DPIs, while LatencyInfo expects
+  // coordinates in device pixels.
+  void set_device_scale_factor(float device_scale_factor) {
+    device_scale_factor_ = device_scale_factor;
+  }
+
+  // Returns the ID that uniquely describes this component to the latency
+  // subsystem.
+  int64 latency_component_id() const { return latency_component_id_; }
+
+ private:
+  int64 last_event_id_;
+  int64 latency_component_id_;
+  float device_scale_factor_;
+
+  DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostLatencyTracker);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_LATENCY_TRACKER_H_