MouseWheelEventQueue should respect ScrollBegin/End state from RenderWidgetHost.

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index 8f605720ea04f61beb112b06d549c9a302687407..76146d3a0533f79379bf46d326a6b57bb3e2b335 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -1101,11 +1101,13 @@ void RenderWidgetHostImpl::ForwardGestureEventWithLatencyInfo(
               blink::WebGestureDevice::kWebGestureDeviceTouchpad
           ? &is_in_touchpad_gesture_scroll_
           : &is_in_touchscreen_gesture_scroll_;
-  if (gesture_event.GetType() == blink::WebInputEvent::kGestureScrollBegin) {
+  if (gesture_event.GetType() == blink::WebInputEvent::kGestureScrollBegin &&
+      !gesture_event.data.scroll_begin.synthetic) {
     DCHECK(!(*is_in_gesture_scroll));
     *is_in_gesture_scroll = true;
-  } else if (gesture_event.GetType() ==
-                 blink::WebInputEvent::kGestureScrollEnd ||
+  } else if ((gesture_event.GetType() ==

[dtapuska, 2017/04/13 13:39:47]

So does this cause a weird state due scroll ends bubbling
https://cs.chromium.org/chromium/src/content/browser/frame_host/cross_process...


I have a
GSB
GSU
GSE (synthetic)
GSB (synthetic)
GSU
GSE


The child frame would see:

GSB (generated in RWHI)
GSU (bubbled)
GSE (synthetic bubbled)
GSU (bubbled)
GSE 

Note you are getting a GSU without a GSB.

[wjmaclean, 2017/04/13 14:17:11]

Hmm, I didn't realize that there would be synthetic GSB/E's injected into the
stream.

Fwiw, it seems to work fine with the current patch, though I haven't done manual
testing on Mac (though OOPIF scroll bubbling is already broken in other ways
there).

Once latching is enabled (in RWHIER), we can presumably do away with all this
logic anyways.

We can try having the OOPIF just forward all the GSB/U/Es that it sees ... do
you think that would work? Will it work if we scroll across the boundary between
an OOPIF and its parent?

+                  blink::WebInputEvent::kGestureScrollEnd &&
+              !gesture_event.data.scroll_end.synthetic) ||
              gesture_event.GetType() ==
                  blink::WebInputEvent::kGestureFlingStart) {
     // TODO(wjmaclean): Re-enable the following DCHECK once crbug.com/695187
@@ -1147,6 +1149,19 @@ void RenderWidgetHostImpl::ForwardGestureEventWithLatencyInfo(
   }
 }
 
+bool RenderWidgetHostImpl::IsInGestureScroll(
+    blink::WebGestureDevice device) const {
+  switch (device) {
+    case blink::WebGestureDevice::kWebGestureDeviceTouchpad:
+      return is_in_touchpad_gesture_scroll_;
+    case blink::WebGestureDevice::kWebGestureDeviceTouchscreen:
+      return is_in_touchscreen_gesture_scroll_;
+    default:
+      NOTREACHED();
+      return false;  // Required to keep the compiler happy.
+  }
+}
+
 void RenderWidgetHostImpl::ForwardEmulatedTouchEvent(
       const blink::WebTouchEvent& touch_event) {
   TRACE_EVENT0("input", "RenderWidgetHostImpl::ForwardEmulatedTouchEvent");