Pass MotionEvent tilt angles to Blink on Android.

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 b389600f23b33709d46b444a4dcb420368403f6b..d250b18988e2c58c2c4d71859cc6ce16b913e9fd 100644
--- a/ui/events/blink/blink_event_util.cc
+++ b/ui/events/blink/blink_event_util.cc
@@ -99,21 +99,28 @@ WebTouchPoint CreateWebTouchPoint(const MotionEvent& event,
   DCHECK_LE(minor_radius, major_radius);
   DCHECK_IMPLIES(major_radius, minor_radius);
 
-  float orientation_deg = event.GetOrientation(pointer_index) * 180.f / M_PI;
+  float orientation_rad = event.GetOrientation(pointer_index);
+  float orientation_deg = orientation_rad * 180.f / M_PI;
   DCHECK_GE(major_radius, 0);
   DCHECK_GE(minor_radius, 0);
   DCHECK_GE(major_radius, minor_radius);
   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;
+
+    // A stylus points to a direction specified by orientation and tilts to
+    // the opposite direction. Coordinate system is left-handed.
+    float tilt_rad = event.GetTilt(pointer_index);
+    float r = sin(tilt_rad);
+    float z = cos(tilt_rad);
+    touch.tiltX = atan2(sin(-orientation_rad) * r, z) * 180.f / M_PI;
+    touch.tiltY = atan2(cos(-orientation_rad) * r, z) * 180.f / M_PI;
   } else {
     // Orientation lies in [-90, 90] for a touch. Normalise to [-90, 90).
     // Allow a small bound tolerance to account for floating point conversion.
@@ -121,6 +128,8 @@ WebTouchPoint CreateWebTouchPoint(const MotionEvent& event,
     DCHECK_LT(orientation_deg, 90.01f);
     if (orientation_deg >= 90.f)
       orientation_deg -= 180.f;
+
+    touch.tiltX = touch.tiltY = 0;
   }
   if (orientation_deg >= 0) {
     // The case orientation_deg == 0 is handled here on purpose: although the