Pass MotionEvent tilt angles to Blink on Android.

content/browser/renderer_host/input/motion_event_web.cc

Index: content/browser/renderer_host/input/motion_event_web.cc
diff --git a/content/browser/renderer_host/input/motion_event_web.cc b/content/browser/renderer_host/input/motion_event_web.cc
index 82b6ed7861b6cd2c5c3fbe0fe8cc853b8d7c7772..eeb2124901acd3de0185911b4f57b1f089731767 100644
--- a/content/browser/renderer_host/input/motion_event_web.cc
+++ b/content/browser/renderer_host/input/motion_event_web.cc
@@ -130,26 +130,58 @@ float MotionEventWeb::GetTouchMinor(size_t pointer_index) const {
 float MotionEventWeb::GetOrientation(size_t pointer_index) const {
   DCHECK_LT(pointer_index, GetPointerCount());
 
-  float rotation_angle_rad = event_.touches[pointer_index].rotationAngle
+  float orientation_rad = event_.touches[pointer_index].rotationAngle
       * M_PI / 180.f;
-  DCHECK(0 <= rotation_angle_rad && rotation_angle_rad <= M_PI_2)
+  DCHECK(0 <= orientation_rad && orientation_rad <= M_PI_2)
       << "Unexpected touch rotation angle";
 
-  if (event_.touches[pointer_index].radiusX
-      > event_.touches[pointer_index].radiusY) {
+  if (GetToolType(pointer_index) == TOOL_TYPE_STYLUS) {
+    const WebPointerProperties& pointer = event_.touches[pointer_index];
+

[jdduke (slow), 2015/08/12 17:00:12]

I think we'll want some basic test coverage for this. Doesn't need to be
exhaustive, but we should have at least a couple smoke test cases.

+    if (pointer.tiltY < 0) {
+      if (pointer.tiltX < 0)
+        orientation_rad += M_PI_2;
+      else
+        orientation_rad -= M_PI;
+    } else {
+      if (pointer.tiltX > 0)
+        orientation_rad -= M_PI_2;
+    }
+  } else if (event_.touches[pointer_index].radiusX
+             > event_.touches[pointer_index].radiusY) {
     // The case radiusX == radiusY is omitted from here on purpose: for circles,
     // we want to pass the angle (which could be any value in such cases but
     // always seem to be set to zero) unchanged.
-    rotation_angle_rad -= (float) M_PI_2;
+    orientation_rad -= (float) M_PI_2;
   }
 
-  return rotation_angle_rad;
+  return orientation_rad;
 }
 
 float MotionEventWeb::GetPressure(size_t pointer_index) const {
   return 0.f;
 }
 
+float MotionEventWeb::GetTilt(size_t pointer_index) const {
+  DCHECK_LT(pointer_index, GetPointerCount());
+
+  if (GetToolType(pointer_index) != TOOL_TYPE_STYLUS)
+    return 0.f;
+

[jdduke (slow), 2015/08/12 17:00:13]

Same here, a few basic test cases would be nice. We haven't added tests for this
class until now as most of the getters are trivial, but it's probably time we
add some coverage.

Ideally we'd have a case where we construct a MotionEventGeneric with some
tilt/orientation values, we run that through
CreateWebTouchEventFromMotionEvent(), then create a MotionEventWeb from the
result. The result of GetTilt/GetOrientation should be the same.

+  const WebPointerProperties& pointer = event_.touches[pointer_index];
+
+  float tilt_x_r = sin(pointer.tiltX * M_PI / 180.f);
+  float tilt_x_z = cos(pointer.tiltX * M_PI / 180.f);
+  float tilt_y_r = sin(pointer.tiltY * M_PI / 180.f);
+  float tilt_y_z = cos(pointer.tiltY * M_PI / 180.f);
+  float r_x = tilt_x_r * tilt_y_z;
+  float r_y = tilt_y_r * tilt_x_z;
+  float r = sqrt(r_x * r_x + r_y * r_y);
+  float z = tilt_x_z * tilt_y_z;
+
+  return atan2(r, z);
+}
+
 base::TimeTicks MotionEventWeb::GetEventTime() const {
   return base::TimeTicks() +
          base::TimeDelta::FromMicroseconds(event_.timeStampSeconds *