The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c007949541f4d2238c9653a4e3b8dbc0987bc752

commit c007949541f4d2238c9653a4e3b8dbc0987bc752
Author: lanwei <lanwei@chromium.org>
Date: Fri Apr 28 15:06:21 2017

Make sure PointerEvents's isPrimary set correctly for stylus

When a pen enters and leaves a tablet's proximity and enters again, the
PointerEvents' isPrimary should always be true.

Testing page: https://patrickhlauke.github.io/touch/tracker/multi-touch-tracker-pointer-hud.html

Webplatform test pointerevent_pointerleave_pen-manual.html does not work
right now because of no support of PointerLeave events when pen leaves
the range of the tablet in PointerActionSequence API. I will add it soon.

BUG= 713745 

Review-Url: https://codereview.chromium.org/2831933002
Cr-Commit-Position: refs/heads/master@{#467997}

[modify] https://crrev.com/c007949541f4d2238c9653a4e3b8dbc0987bc752/third_party/WebKit/LayoutTests/external/wpt/pointerevents/pointerevent_pointerleave_pen-manual.html
[modify] https://crrev.com/c007949541f4d2238c9653a4e3b8dbc0987bc752/third_party/WebKit/LayoutTests/external/wpt_automation/pointerevents/pointerevent_pointerleave_pen-manual-automation.js
[modify] https://crrev.com/c007949541f4d2238c9653a4e3b8dbc0987bc752/third_party/WebKit/Source/core/input/PointerEventManager.cpp