Synthetic pinch gesture take scale factor as parameter.

content/browser/renderer_host/input/synthetic_gesture_target_aura.cc

Index: content/browser/renderer_host/input/synthetic_gesture_target_aura.cc
diff --git a/content/browser/renderer_host/input/synthetic_gesture_target_aura.cc b/content/browser/renderer_host/input/synthetic_gesture_target_aura.cc
index 9825cb5c5f9c509fa6ddcdb1eb468206b42dd5ed..0b4d9c8c97f6ed279874415b5d2e5a53bc7a3a17 100644
--- a/content/browser/renderer_host/input/synthetic_gesture_target_aura.cc
+++ b/content/browser/renderer_host/input/synthetic_gesture_target_aura.cc
@@ -132,12 +132,16 @@ SyntheticGestureTargetAura::GetDefaultSyntheticGestureSourceType() const {
   return SyntheticGestureParams::TOUCH_INPUT;
 }
 
-int SyntheticGestureTargetAura::GetTouchSlopInDips() const {
+float SyntheticGestureTargetAura::GetTouchSlopInDips() const {
   // - 1 because Aura considers a pointer to be moving if it has moved at least
   // 'max_touch_move_in_pixels_for_click' pixels.
   return ui::GestureConfiguration::max_touch_move_in_pixels_for_click() - 1;
 }
 
+float SyntheticGestureTargetAura::GetMinScalingSpanInDips() const {
+  return ui::GestureConfiguration::min_distance_for_pinch_scroll_in_pixels();
+}
+
 aura::Window* SyntheticGestureTargetAura::GetWindow() const {
   aura::Window* window = render_widget_host()->GetView()->GetNativeView();
   DCHECK(window);