Move Singleton and related structs to namespace base

ui/events/gesture_detection/gesture_configuration_aura.cc

 // 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.
 
 #include "ui/events/gesture_detection/gesture_configuration.h"
 
 #include "base/command_line.h"
 #include "base/memory/singleton.h"
 #include "ui/events/event_switches.h"
 
 namespace ui {
 namespace {
 
 class GestureConfigurationAura : public GestureConfiguration {
  public:
   ~GestureConfigurationAura() override {
   }
 
   static GestureConfigurationAura* GetInstance() {
-    return Singleton<GestureConfigurationAura>::get();
+    return base::Singleton<GestureConfigurationAura>::get();
   }
 
  private:
   GestureConfigurationAura() : GestureConfiguration() {
     set_double_tap_enabled(false);
     set_double_tap_timeout_in_ms(semi_long_press_time_in_ms());
     set_gesture_begin_end_types_enabled(true);
     set_min_gesture_bounds_length(default_radius());
     set_min_pinch_update_span_delta(
         base::CommandLine::ForCurrentProcess()->HasSwitch(
             switches::kCompensateForUnstablePinchZoom)
             ? 5
             : 0);
     set_min_scaling_touch_major(default_radius() * 2);
     set_velocity_tracker_strategy(VelocityTracker::Strategy::LSQ2_RESTRICTED);
     set_span_slop(max_touch_move_in_pixels_for_click() * 2);
     set_swipe_enabled(true);
     set_two_finger_tap_enabled(true);
     set_fling_touchpad_tap_suppression_enabled(true);
     set_fling_touchscreen_tap_suppression_enabled(true);
   }
 
-  friend struct DefaultSingletonTraits<GestureConfigurationAura>;
+  friend struct base::DefaultSingletonTraits<GestureConfigurationAura>;
   DISALLOW_COPY_AND_ASSIGN(GestureConfigurationAura);
 };
 
 }  // namespace
 
 // Create a GestureConfigurationAura singleton instance when using aura.
 GestureConfiguration* GestureConfiguration::GetPlatformSpecificInstance() {
   return GestureConfigurationAura::GetInstance();
 }
 
 }  // namespace ui