Histogram for gesture events being dropped based on allowed touch action.

Added an UMA_HISTOGRAM_BOOLEAN to report how often a gesture event is
or is not dropped based on the current touch action state not
matching the gesture event.

Bug: 745718
Change-Id: Ib1c9f91cfcaa846f3e8bba9a7b1c87f698b2a962
Reviewed-on: https://chromium-review.googlesource.com/575071
Commit-Queue: Xida Chen <xidachen@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488296}

content/browser/renderer_host/input/touch_action_filter.cc

@@ -7,6 +7,7 @@
 #include <math.h>
 
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
 #include "third_party/WebKit/public/platform/WebGestureEvent.h"
 
 using blink::WebInputEvent;
@@ -25,6 +26,12 @@ bool IsXAxisActionDisallowed(cc::TouchAction action) {
   return (action & cc::kTouchActionPanY) && !(action & cc::kTouchActionPanX);
 }
 
+// Report how often the gesture event is or is not dropped due to the current
+// allowed touch action state not matching the gesture event.
+void ReportGestureEventFiltered(bool event_filtered) {
+  UMA_HISTOGRAM_BOOLEAN("TouchAction.GestureEventFiltered", event_filtered);
+}
+
 }  // namespace
 
 TouchActionFilter::TouchActionFilter()
@@ -69,6 +76,7 @@ bool TouchActionFilter::FilterGestureEvent(WebGestureEvent* gesture_event) {
       break;
 
     case WebInputEvent::kGestureFlingStart:
+      ReportGestureEventFiltered(suppress_manipulation_events_);
       // Touchscreen flings should always have non-zero velocity.
       DCHECK(gesture_event->data.fling_start.velocity_x ||
              gesture_event->data.fling_start.velocity_y);
@@ -89,11 +97,13 @@ bool TouchActionFilter::FilterGestureEvent(WebGestureEvent* gesture_event) {
       return FilterManipulationEventAndResetState();
 
     case WebInputEvent::kGestureScrollEnd:
+      ReportGestureEventFiltered(suppress_manipulation_events_);
       return FilterManipulationEventAndResetState();
 
     case WebInputEvent::kGesturePinchBegin:
     case WebInputEvent::kGesturePinchUpdate:
     case WebInputEvent::kGesturePinchEnd:
+      ReportGestureEventFiltered(suppress_manipulation_events_);
       return suppress_manipulation_events_;
 
     // The double tap gesture is a tap ending event. If a double tap gesture is

tools/metrics/histograms/enums.xml

@@ -36968,6 +36968,11 @@ from previous Chrome versions.
   <int value="3" label="Disabled"/>
 </enum>
 
+<enum name="TouchGestureEventFiltered">
+  <int value="0" label="Touch gesture event not filtered"/>
+  <int value="1" label="Touch gesture event filtered"/>
+</enum>
+
 <enum name="TouchpadDeviceState">
   <int value="0" label="NO_TP_PRESENT_NO_TP_EXPECTED">
     No touchpad detected on a device without built-in touchpad

tools/metrics/histograms/histograms.xml

@@ -80413,6 +80413,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="TouchAction.GestureEventFiltered"
+    enum="TouchGestureEventFiltered">
+  <owner>hayleyferr@chromium.org</owner>
+  <owner>xidachen@chromium.org</owner>
+  <summary>
+    Tracks how often a gesture event is or is not dropped due to the current
+    allowed touch action state not matching the gesture event.
+  </summary>
+</histogram>
+
 <histogram name="TouchBar.Default.Metrics" enum="DefaultTouchBarActions">
   <owner>spqchan@chromium.com</owner>
   <summary>Tracks the usage of the default touch bar buttons.</summary>