Pressure should not be set when the pointer device doesn't support pressure

content/browser/renderer_host/input/web_input_event_builders_mac.mm

Index: content/browser/renderer_host/input/web_input_event_builders_mac.mm
diff --git a/content/browser/renderer_host/input/web_input_event_builders_mac.mm b/content/browser/renderer_host/input/web_input_event_builders_mac.mm
index d9cf15370d0d376278a578286087fb56a0d673a0..45c37416b0d02e754e0700ceaed613b8fbff8bc2 100644
--- a/content/browser/renderer_host/input/web_input_event_builders_mac.mm
+++ b/content/browser/renderer_host/input/web_input_event_builders_mac.mm
@@ -405,17 +405,22 @@ blink::WebMouseEvent WebMouseEventBuilder::Build(NSEvent* event, NSView* view) {
   // 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::Pen;
-  } else {
+  if (subtype != NSTabletPointEventSubtype &&
+      subtype != NSTabletProximityEventSubtype) {
     result.pointerType = blink::WebPointerProperties::PointerType::Mouse;
+    return result;

[mustaq, 2016/09/21 19:39:36]

- Could you please confirm that uninitialized result.force gets a NaN value here
as opposed to 0 or random? For result.tiltX/Y, uninitialized values are always
0, right?

- You are now setting the value by relying on pointerType. Is there a way to
query the device if pressure is supported or not? If not sure, please add a
TODO.

[lanwei, 2016/09/21 20:13:42]

Yes, default values of force is NaN, tiltx, y are 0,
https://codesearch.chromium.org/chromium/src/third_party/WebKit/public/platfo...

There is no way to query a specific property, in their spec, they said we can
use the subtype to decide if the event is 'pointer events', the event that a
tablet device generates after a stylus has entered proximity of the tablet, the
pressure, rotation, tilt are defined under this event.

   }
+
+  // Set stylus properties for events with a subtype of
+  // NSTabletPointEventSubtype.
+  result.pointerType = blink::WebPointerProperties::PointerType::Pen;
   result.id = [event deviceID];
-  result.force = [event pressure];
-  NSPoint tilt = [event tilt];
-  result.tiltX = lround(tilt.x * 90);
-  result.tiltY = lround(tilt.y * 90);
+  if (subtype == NSTabletPointEventSubtype) {
+    result.force = [event pressure];
+    NSPoint tilt = [event tilt];
+    result.tiltX = lround(tilt.x * 90);
+    result.tiltY = lround(tilt.y * 90);
+  }
   return result;
 }