x11: Use kernel timestamps for touch events (if available).

BUG=153450

Review URL: https://chromiumcodereview.appspot.com/10868100

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@161396 0039d316-1c4b-4281-b951-d872f2087c98

ui/base/x/events_x.cc

@@ -803,9 +803,13 @@ base::TimeDelta EventTimeFromNative(const base::NativeEvent& native_event) {
       break;
     case GenericEvent: {
       double start, end;
+      float touch_timestamp;
       if (GetGestureTimes(native_event, &start, &end)) {
         // If the driver supports gesture times, use them.
         return base::TimeDelta::FromMicroseconds(end * 1000000);
+      } else if (ValuatorTracker::GetInstance()->ExtractValuator(*native_event,
+                 ValuatorTracker::VAL_TOUCH_RAW_TIMESTAMP, &touch_timestamp)) {
+        return base::TimeDelta::FromMicroseconds(touch_timestamp * 1000000);
       } else {
         XIDeviceEvent* xide =
             static_cast<XIDeviceEvent*>(native_event->xcookie.data);

ui/base/x/valuators.cc

@@ -18,6 +18,7 @@ namespace {
 #define AXIS_LABEL_ABS_MT_PRESSURE    "Abs MT Pressure"
 #define AXIS_LABEL_ABS_MT_SLOT_ID     "Abs MT Slot ID"
 #define AXIS_LABEL_ABS_MT_TRACKING_ID "Abs MT Tracking ID"
+#define AXIS_LABEL_TOUCH_TIMESTAMP    "Touch Timestamp"
 
 // Given the Valuator, return the correspoding XIValuatorClassInfo using
 // the X device information through Atom name matching.
@@ -47,6 +48,8 @@ XIValuatorClassInfo* FindValuator(Display* display,
 #endif
     { ui::ValuatorTracker::VAL_TRACKING_ID,
       XInternAtom(ui::GetXDisplay(), AXIS_LABEL_ABS_MT_TRACKING_ID, false) },
+    { ui::ValuatorTracker::VAL_TOUCH_RAW_TIMESTAMP,
+      XInternAtom(ui::GetXDisplay(), AXIS_LABEL_TOUCH_TIMESTAMP, false) },
     { ui::ValuatorTracker::VAL_LAST_ENTRY, None },
   };
 

ui/base/x/valuators.h

@@ -55,6 +55,9 @@ class UI_EXPORT ValuatorTracker {
     // the numerical limit.
     VAL_TRACKING_ID,       // ID of the touch point.
 
+    // Kernel timestamp from touch screen (if available).
+    VAL_TOUCH_RAW_TIMESTAMP,
+
     VAL_LAST_ENTRY
   };