Validate that ui::Event::time_stamp comes from the same clock as TimeTicks::Now

ui/events/x/events_x_utils.cc

 // Copyright (c) 2016 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.
 
 #include "ui/events/x/events_x_utils.h"
 
 #include <stddef.h>
 #include <string.h>
 #include <X11/extensions/XInput.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/XKBlib.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
 #include <cmath>
 
-#include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/singleton.h"
 #include "base/metrics/histogram_macros.h"
 #include "build/build_config.h"
 #include "ui/display/display.h"
 #include "ui/display/screen.h"
 #include "ui/events/base_event_utils.h"
 #include "ui/events/devices/x11/device_data_manager_x11.h"
 #include "ui/events/devices/x11/device_list_cache_x11.h"
@@ skipping 276 matching lines @@
   if (!end_time)
     end_time = &end_time_;
 
   ui::DeviceDataManagerX11::GetInstance()->GetGestureTimes(xev, start_time,
                                                            end_time);
   return true;
 }
 
 int64_t g_last_seen_timestamp_ms = 0;
 int64_t g_rollover_ms = 0;
-bool g_bogus_x11_timestamps = false;
-base::LazyInstance<std::unique_ptr<base::TickClock>>::Leaky g_tick_clock =
-    LAZY_INSTANCE_INITIALIZER;
 
 // Takes Xlib Time and returns a time delta that is immune to timer rollover.
 // This function is not thread safe as we do not use a lock.
 base::TimeTicks TimeTicksFromXEventTime(Time timestamp) {
   int64_t timestamp64 = timestamp;
 
   if (!timestamp)
-    return base::TimeTicks();
-
-  if (g_bogus_x11_timestamps)
-    return base::TimeTicks::Now();
+    return ui::EventTimeForNow();
 
   // If this is the first event that we get, assume the time stamp roll-over
   // might have happened before the process was started.
   // Register a rollover if the distance between last timestamp and current one
   // is larger than half the width. This avoids false rollovers even in a case
   // where X server delivers reasonably close events out-of-order.
   bool had_recent_rollover =
       !g_last_seen_timestamp_ms ||
       g_last_seen_timestamp_ms - timestamp64 > (UINT32_MAX >> 1);
 
   g_last_seen_timestamp_ms = timestamp64;
   if (!had_recent_rollover)
     return base::TimeTicks() +
-           base::TimeDelta::FromMilliseconds(g_rollover_ms + timestamp);
+        base::TimeDelta::FromMilliseconds(g_rollover_ms + timestamp);
 
   DCHECK(timestamp64 <= UINT32_MAX)
       << "X11 Time does not roll over 32 bit, the below logic is likely wrong";
 
-  base::TimeTicks now_ticks = g_tick_clock.Get() != nullptr
-                                  ? g_tick_clock.Get()->NowTicks()
-                                  : base::TimeTicks::Now();
+  base::TimeTicks now_ticks = ui::EventTimeForNow();
   int64_t now_ms = (now_ticks - base::TimeTicks()).InMilliseconds();
 
   g_rollover_ms = now_ms & ~static_cast<int64_t>(UINT32_MAX);
   uint32_t delta = static_cast<uint32_t>(now_ms - timestamp);
-  if (!g_tick_clock.Get()) {
-    if (delta > 60 * 1000) {
-      // x11 timestamps don't seem to be using the same time base as TimeTicks,
-      // so ignore them altogether and always use current time instead.
-      delta = 0;
-      g_bogus_x11_timestamps = true;
-      LOG(WARNING)
-          << "Unexpected x11 timestamps, will use browser time instead.";
-    }
-    UMA_HISTOGRAM_BOOLEAN("Event.TimestampHasValidTimebase",
-                          !g_bogus_x11_timestamps);
-  }
-
   return base::TimeTicks() + base::TimeDelta::FromMilliseconds(now_ms - delta);
 }
 
 }  // namespace
 
 namespace ui {
 
 EventType EventTypeFromXEvent(const XEvent& xev) {
   // Allow the DeviceDataManager to block the event. If blocked return
   // ET_UNKNOWN as the type so this event will not be further processed.
@@ skipping 444 matching lines @@
 
   DeviceDataManagerX11::GetInstance()->GetFlingData(xev, vx, vy, vx_ordinal,
                                                     vy_ordinal, is_cancel);
   return true;
 }
 
 void ResetTimestampRolloverCountersForTesting(
     std::unique_ptr<base::TickClock> tick_clock) {
   g_last_seen_timestamp_ms = 0;
   g_rollover_ms = 0;
-  g_bogus_x11_timestamps = false;
-  g_tick_clock.Get() = std::move(tick_clock);
+  SetEventTickClockForTesting(std::move(tick_clock));
 }
 
 }  // namespace ui