Fix motion event orientation handling for styluses.

ui/events/blink/blink_event_util.cc

Index: ui/events/blink/blink_event_util.cc
diff --git a/ui/events/blink/blink_event_util.cc b/ui/events/blink/blink_event_util.cc
index 9a3a648ae3306e5517b87255acd1c5d0f1fac847..47ed7873c763e6f3754e7c8e90312e0dc7b905c8 100644
--- a/ui/events/blink/blink_event_util.cc
+++ b/ui/events/blink/blink_event_util.cc
@@ -103,9 +103,15 @@ WebTouchPoint CreateWebTouchPoint(const MotionEvent& event,
   DCHECK_GE(major_radius, 0);
   DCHECK_GE(minor_radius, 0);
   DCHECK_GE(major_radius, minor_radius);
+  // Orientation lies in [-90, 90] for a touch screen or pad and in [-180, 180]
+  // for a stylus.
   // Allow a small bound tolerance to account for floating point conversion.
-  DCHECK_GT(orientation_deg, -90.01f);
-  DCHECK_LT(orientation_deg, 90.01f);
+  DCHECK_GT(orientation_deg, -180.01f);

[jdduke (slow), 2015/05/28 15:01:45]

I spoke offline with mustaq/tdresser. We decided it might be simplest for us to
proceed with this solution, however, we should restrict the validation to match
the Android spec. So this will look like:

if (event.GetToolType(pointer_index) == MotionEvent::TOOL_TYPE_STYLUS) {
  *insert code you have now*
} else {
  * insert old [90, 90] validation code *
}

[USE eero AT chromium.org, 2015/05/29 10:49:30]

Done.

+  DCHECK_LT(orientation_deg, 180.01f);
+  if (orientation_deg >= 90.f)

[jdduke (slow), 2015/05/28 15:01:45]

Let's make this a strict inequality (>, <).

[USE eero AT chromium.org, 2015/05/29 10:49:30]

Actually, this one should not be a strict inequality.
According to the TouchEvent spec, rotationAngle must be less than (and not equal
to) 90.

+    orientation_deg -= 180.f;
+  if (orientation_deg <= -90.f)

[USE eero AT chromium.org, 2015/05/29 10:49:30]

But this should be a strict inequality.
Done.

+    orientation_deg += 180.f;
   if (orientation_deg >= 0) {
     // The case orientation_deg == 0 is handled here on purpose: although the
     // 'else' block is equivalent in this case, we want to pass the 0 value