Adopt ui::GestureConfiguration on Android

ui/events/gesture_detection/gesture_configuration_android.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 "ui/gfx/android/view_configuration.h"
+#include "ui/gfx/screen.h"
+
+using gfx::ViewConfiguration;
+
+namespace ui {
+
+class GestureConfigurationAndroid : public GestureConfiguration {

[jdduke (slow), 2014/10/21 15:17:12]

Nit: This class can be put in an anonymous namespace, 

namespace {

class GestureConfigurationAndroid : ...

}  // namespace

GestureConfiguration* GestureConfiguration::GetInstance() {

...

[lanwei, 2014/10/21 20:52:31]

Done.

+ public:
+  static GestureConfigurationAndroid* GetInstance() {
+    return Singleton<GestureConfigurationAndroid>::get();
+  }
+
+  GestureProvider::Config DefaultGestureProviderConfig() {
+    GestureProvider::Config config;
+    config.display = gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
+    config.gesture_detector_config = DefaultGestureDetectorConfig();
+    config.scale_gesture_detector_config = DefaultScaleGestureDetectorConfig();
+    config.gesture_begin_end_types_enabled = false;
+    config.min_gesture_bounds_length = kMinGestureBoundsLengthDips;

[jdduke (slow), 2014/10/21 15:17:12]

Nit: Prefer non-member constants, so |k{Min,Max|GestureBoundsLengthDips| should
go above in an anonymous namespace.

[lanwei, 2014/10/21 20:52:31]

Done.

+    config.max_gesture_bounds_length = kMaxGestureBoundsLengthDips;
+    return config;
+  }
+
+ private:
+  GestureConfigurationAndroid() : GestureConfiguration() {
+    set_long_press_time_in_ms(ViewConfiguration::GetLongPressTimeoutInMs());
+    set_semi_long_press_time_in_ms(
+        ViewConfiguration::GetDoubleTapTimeoutInMs());
+    set_show_press_delay_in_ms(ViewConfiguration::GetTapTimeoutInMs());
+    set_fling_velocity_cap(
+        ViewConfiguration::GetMaximumFlingVelocityInPixelsPerSecond() *
+        GetRawPixelToDIPRatio());
+    set_min_scroll_velocity(
+        ViewConfiguration::GetMinimumFlingVelocityInPixelsPerSecond() *
+        GetRawPixelToDIPRatio());
+    set_max_touch_move_in_pixels_for_click(
+        ViewConfiguration::GetTouchSlopInPixels() * GetRawPixelToDIPRatio());
+    set_max_distance_between_taps_for_double_tap(
+        ViewConfiguration::GetDoubleTapSlopInPixels() *
+        GetRawPixelToDIPRatio());
+    set_span_slop(ViewConfiguration::GetTouchSlopInPixels() * 2.f *
+                  GetRawPixelToDIPRatio());
+    set_min_scaling_touch_major(
+        ViewConfiguration::GetMinScalingTouchMajorInPixels() *
+        GetRawPixelToDIPRatio());
+    set_min_scaling_span_in_pixels(
+        ViewConfiguration::GetMinScalingSpanInPixels() *
+        GetRawPixelToDIPRatio());
+    set_min_pinch_update_span_delta(0.f);
+  }
+
+  friend struct DefaultSingletonTraits<GestureConfigurationAndroid>;
+  const gfx::Display GetDisplay() {

[jdduke (slow), 2014/10/21 15:17:12]

Nit: I would get rid of both of these helper functions, instead, just cache a
|pixel_to_dip| constant at the top of the GestureConfigurationAndroid()
constructor.

[lanwei, 2014/10/21 20:52:31]

Done.

+    return gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
+  }
+
+  const float GetRawPixelToDIPRatio() {
+    return 1.f / GetDisplay().device_scale_factor();
+  }
+  // This was the minimum tap/press size used on Android before the new gesture
+  // detection pipeline.
+  const float kMinGestureBoundsLengthDips = 24.f;
+
+  // This value is somewhat arbitrary, but provides a reasonable maximum
+  // approximating a large thumb depression.
+  const float kMaxGestureBoundsLengthDips = kMinGestureBoundsLengthDips * 4.f;
+
+  DISALLOW_COPY_AND_ASSIGN(GestureConfigurationAndroid);
+};
+
+GestureConfiguration* GestureConfiguration::GetInstance() {
+  return GestureConfigurationAndroid::GetInstance();
+}
+
+GestureProvider::Config DefaultGestureProviderConfig() {
+  return GestureConfigurationAndroid::GetInstance()
+      ->DefaultGestureProviderConfig();
+}
+
+}  // namespace ui