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..b389600f23b33709d46b444a4dcb420368403f6b 100644
--- a/ui/events/blink/blink_event_util.cc
+++ b/ui/events/blink/blink_event_util.cc
@@ -103,9 +103,25 @@ WebTouchPoint CreateWebTouchPoint(const MotionEvent& event,
   DCHECK_GE(major_radius, 0);
   DCHECK_GE(minor_radius, 0);
   DCHECK_GE(major_radius, minor_radius);
-  // Allow a small bound tolerance to account for floating point conversion.
-  DCHECK_GT(orientation_deg, -90.01f);
-  DCHECK_LT(orientation_deg, 90.01f);
+  if (event.GetToolType(pointer_index) == MotionEvent::TOOL_TYPE_STYLUS) {
+    // Orientation lies in [-180, 180] for a stylus. Normalise to [-90, 90).
+    // Allow a small bound tolerance to account for floating point conversion.
+    // TODO(e_hakkinen): crbug.com/493728: Pass also unaltered orientation
+    //                   to touch in order not to lose quadrant information.
+    DCHECK_GT(orientation_deg, -180.01f);
+    DCHECK_LT(orientation_deg, 180.01f);
+    if (orientation_deg >= 90.f)
+      orientation_deg -= 180.f;
+    else if (orientation_deg < -90.f)
+      orientation_deg += 180.f;
+  } else {
+    // Orientation lies in [-90, 90] for a touch. Normalise to [-90, 90).
+    // Allow a small bound tolerance to account for floating point conversion.
+    DCHECK_GT(orientation_deg, -90.01f);
+    DCHECK_LT(orientation_deg, 90.01f);
+    if (orientation_deg >= 90.f)
+      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