Animated scroll shouldn't consume unhandled scrolls for OOPIFs.

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index c6c682fa6e90c08649c1d8bf22a845ae0c4683ce..30d0b40c4a99f7281d28805b7995cb8d430d640c 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -296,12 +296,6 @@ class CONTENT_EXPORT RenderWidgetHostImpl : public RenderWidgetHost,
   // Notifies the RenderWidgetHost that the View was destroyed.
   void ViewDestroyed();
 
-  // Signals if this host has forwarded a GestureScrollBegin without yet having
-  // forwarded a matching GestureScrollEnd/GestureFlingStart.
-  bool is_in_touchscreen_gesture_scroll() const {
-    return is_in_touchscreen_gesture_scroll_;
-  }
-
 #if defined(OS_MACOSX)
   // Pause for a moment to wait for pending repaint or resize messages sent to
   // the renderer to arrive. If pending resize messages are for an old window
@@ -358,6 +352,10 @@ class CONTENT_EXPORT RenderWidgetHostImpl : public RenderWidgetHost,
       const blink::WebMouseWheelEvent& wheel_event,
       const ui::LatencyInfo& ui_latency);  // Virtual for testing.
 
+  // Signals if this host has forwarded a GestureScrollBegin without yet having
+  // forwarded a matching GestureScrollEnd/GestureFlingStart.
+  bool is_in_gesture_scroll(blink::WebGestureDevice device) override;

[bokan, 2017/04/11 16:23:14]

Touchscreen and Touchpad gesture event streams can differ for Flings but I can
never remember how. Sahel should confirm that this change is ok.

[sahel, 2017/04/12 15:40:22]

This function is used only for wheel/touchpad scrolling. For 4 combinations of
existence of OOPIFs and scroll propagation vs latching, this logic works for all
except the case that an OOPIF exists and scroll latching is enabled. This case
is broken anyway and regardless of this change we need to fix it.

Touchpad GFS comes after a GSE when wheel scroll latching is disabled
(is_in_gesture_scroll is false), but when latching is enabled, similar to touch,
GFS comes when is_in_gesture_scroll is true. In all cases GFS sets
is_in_gesture_scroll to false.

[bokan, 2017/04/12 19:15:10]

I don't think that's true. Taking a quick look, it was and still is called from
RenderWidgetHostInputEventRouter::RouteTouchscreenGestureEvent.

[sahel, 2017/04/18 15:43:43]

I think is_in_touchscreen_gesture_scroll() is called in
RenderWidgetHostInputEventRouter::RouteTouchscreenGestureEvent rather than
is_in_gesture_scroll(). Maybe it should be changed to this new function, though.

+
   // Enables/disables touch emulation using mouse event. See TouchEmulator.
   void SetTouchEventEmulationEnabled(
       bool enabled, ui::GestureProviderConfigType config_type);