Add touch drag UMA latency metric.

content/browser/renderer_host/input/render_widget_host_latency_tracker.h

Index: content/browser/renderer_host/input/render_widget_host_latency_tracker.h
diff --git a/content/browser/renderer_host/input/render_widget_host_latency_tracker.h b/content/browser/renderer_host/input/render_widget_host_latency_tracker.h
index 633e4e878da43bb4097739ec8f934ec3c227ffd9..f86d628d95384ad11d91d2bd8f3de09e9991c527 100644
--- a/content/browser/renderer_host/input/render_widget_host_latency_tracker.h
+++ b/content/browser/renderer_host/input/render_widget_host_latency_tracker.h
@@ -12,6 +12,7 @@
 #include "base/macros.h"
 #include "content/browser/renderer_host/event_with_latency_info.h"
 #include "content/common/content_export.h"
+#include "content/common/input/input_event_ack_state.h"
 #include "ui/events/latency_info.h"
 
 namespace content {
@@ -27,6 +28,11 @@ class CONTENT_EXPORT RenderWidgetHostLatencyTracker {
   // Called once after the RenderWidgetHost is fully initialized.
   void Initialize(int routing_id, int process_id);
 
+  void ComputeInputLatencyHistograms(blink::WebInputEvent::Type type,
+                                     int64_t latency_component_id,
+                                     const ui::LatencyInfo& latency,
+                                     InputEventAckState ack_result);
+
   // 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).
@@ -38,7 +44,8 @@ class CONTENT_EXPORT RenderWidgetHostLatencyTracker {
   // 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);
+                       ui::LatencyInfo* latency,
+                       InputEventAckState ack_result);
 
   // Populates renderer-created LatencyInfo entries with the appropriate latency
   // component id. Called when the RenderWidgetHost receives a compositor swap
@@ -65,6 +72,12 @@ class CONTENT_EXPORT RenderWidgetHostLatencyTracker {
   int64_t latency_component_id_;
   float device_scale_factor_;
   bool has_seen_first_gesture_scroll_update_;
+  // Whether the current stream of touch events has ever included more than one
+  // touch point.
+  bool multi_finger_gesture_;
+  // Whether the touch start for the current stream of touch events had its
+  // default action prevented. Only valid for single finger gestures.
+  bool touch_start_default_prevented_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostLatencyTracker);
 };