Touchpad scroll latching enabled for Mac behind flag.

ui/events/blink/input_handler_proxy.cc

Index: ui/events/blink/input_handler_proxy.cc
diff --git a/ui/events/blink/input_handler_proxy.cc b/ui/events/blink/input_handler_proxy.cc
index 115c21a9c70a4b281fac7705bfa7520f122e5f4a..c7ecdd0ef197aeb33362f53d48d369833060276c 100644
--- a/ui/events/blink/input_handler_proxy.cc
+++ b/ui/events/blink/input_handler_proxy.cc
@@ -131,6 +131,11 @@ cc::ScrollState CreateScrollStateForGesture(const WebGestureEvent& event) {
       scroll_state_data.position_x = event.x;
       scroll_state_data.position_y = event.y;
       scroll_state_data.is_beginning = true;
+      // On Mac, a GestureScrollBegin in the inertial phase indicates a fling
+      // start.
+      if (event.data.scrollBegin.inertialPhase ==
+          WebGestureEvent::MomentumPhase)

[tdresser, 2016/08/18 16:55:54]

Although this isn't technically required by the style guide, I much prefer {}
when there are multiline conditionals (as well as multiline bodies).

[sahel, 2016/08/18 17:37:59]

Done.

+        scroll_state_data.is_in_inertial_phase = true;
       break;
     case WebInputEvent::GestureFlingStart:
       scroll_state_data.velocity_x = event.data.flingStart.velocityX;