Am I correct that external digitizers (say Wacom Intuos Pro) are fine (IIRC they are perhaps considered indirect-manipulation device in CrOS)?

If I am wrong, this would mean we have practically stopped supporting hovering pens altogether even though browser-side event plumbing is there!  We would need to raise the priority to P1 then.

This test is also failing due to the same situation:
w3c-test.org/pointerevents/pointerevent_sequence_at_implicit_release_on_click-manual.html

Navid I believe you are working on this right?

I am and I don't know why I hadn't assigned it. Thanks.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/abfb81cc59e040553b09254c5a08a186f9700f74

commit abfb81cc59e040553b09254c5a08a186f9700f74
Author: Navid Zolghadr <nzolghadr@chromium.org>
Date: Wed Feb 07 15:59:05 2018

Indicate whether a WebTouchEvent is hovering or not

When pen is touching the digitizer we send touch events
instead of mouse events to get the direct manipulation
behavior such as scroll on drag. However, as oppose to
normal touch when pointerup (or touchend) happens the
pen might still be in the range of the digitizer and
Blink shouldn't just send the out/leave events right
after the up event. So this CL comminucates this
information from the browser to Blink so that it only
sends boundary events after up event when it does not
support hover.

Bug:  805011 
Change-Id: Ifab24950e22a55835ed069955228236d2ec84c9b
Reviewed-on: https://chromium-review.googlesource.com/893802
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Rick Byers <rbyers@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Navid Zolghadr <nzolghadr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535015}
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/content/browser/renderer_host/input/motion_event_web_unittest.cc
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/content/browser/renderer_host/input/web_input_event_util_unittest.cc
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/content/browser/renderer_host/render_widget_host_view_android.cc
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/content/browser/renderer_host/render_widget_host_view_event_handler.cc
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/content/common/input/input_event_struct_traits.cc
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/content/common/input/input_handler.mojom
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/content/shell/test_runner/event_sender.cc
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/third_party/WebKit/Source/core/events/PointerEventFactory.cpp
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/third_party/WebKit/Source/core/events/PointerEventFactory.h
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/third_party/WebKit/Source/core/events/PointerEventFactoryTest.cpp
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/third_party/WebKit/Source/core/input/PointerEventManager.cpp
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/third_party/WebKit/Source/core/input/PointerEventManager.h
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/third_party/WebKit/Source/platform/WebPointerEvent.cpp
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/third_party/WebKit/public/platform/WebPointerEvent.h
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/third_party/WebKit/public/platform/WebTouchEvent.h
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/ui/events/blink/blink_event_util.cc
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/ui/events/blink/blink_event_util.h
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/ui/events/blink/web_input_event_traits.cc
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/ui/events/event.cc
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/ui/events/event.h
[modify] https://crrev.com/abfb81cc59e040553b09254c5a08a186f9700f74/ui/views/win/pen_event_processor.cc