Make stylus's eraser button work on Mac

content/browser/renderer_host/input/web_input_event_builders_mac.mm

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2006-2009 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ skipping 303 matching lines @@
     default:
       NOTIMPLEMENTED();
   }
 
   blink::WebMouseEvent result(event_type, ModifiersFromEvent(event),
                               [event timestamp]);
   result.clickCount = click_count;
   result.button = button;
   SetWebEventLocationFromEventInView(&result, event, view);
 
-  // For NSMouseExited and NSMouseEntered events, they do not have a subtype.
-  // We decide their pointer types by checking if we recevied a
-  // NSTabletProximity event.
-  if (type == NSMouseExited || type == NSMouseEntered) {
-    result.pointerType = pointerType;
-    return result;
-  }
-
-  // For other mouse events and touchpad events, the pointer type is mouse.
-  // For all other tablet events, the pointer type will be just pen.
-  NSEventSubtype subtype = [event subtype];
-  if (subtype != NSTabletPointEventSubtype &&
-      subtype != NSTabletProximityEventSubtype) {
-    result.pointerType = blink::WebPointerProperties::PointerType::Mouse;
+  result.pointerType = pointerType;
+  if ((type == NSMouseExited || type == NSMouseEntered) ||
+      ([event subtype] != NSTabletPointEventSubtype &&
+       [event subtype] != NSTabletProximityEventSubtype)) {
     return result;
   }
 
   // Set stylus properties for events with a subtype of
   // NSTabletPointEventSubtype.
-  result.pointerType = blink::WebPointerProperties::PointerType::Pen;
+  NSEventSubtype subtype = [event subtype];
   result.id = [event deviceID];
   if (subtype == NSTabletPointEventSubtype) {
     result.force = [event pressure];
     NSPoint tilt = [event tilt];
     result.tiltX = lround(tilt.x * 90);
     result.tiltY = lround(tilt.y * 90);
     result.tangentialPressure = [event tangentialPressure];
     // NSEvent spec doesn't specify the range of rotation, we make sure that
     // this value is in the range of [0,359].
     int twist = (int)[event rotation];
@@ skipping 195 matching lines @@
       // to specify them when the gesture is differentiated.
       break;
     default:
       NOTIMPLEMENTED();
   }
 
   return result;
 }
 
 }  // namespace content