VR: Improve scrolling

chrome/browser/android/vr_shell/vr_controller.h

Index: chrome/browser/android/vr_shell/vr_controller.h
diff --git a/chrome/browser/android/vr_shell/vr_controller.h b/chrome/browser/android/vr_shell/vr_controller.h
index 7580500332ecf5ba8818b980521724078578941a..44f0aab27dfd8a10fb51c9bbdc82f84995ca0889 100644
--- a/chrome/browser/android/vr_shell/vr_controller.h
+++ b/chrome/browser/android/vr_shell/vr_controller.h
@@ -129,9 +129,14 @@ class VrController {
   float last_qx_;
   bool pinch_started_;
   bool zoom_in_progress_ = false;
+  bool touch_position_changed_ = false;
 
+  // Current touch info after the extrapolation.
   std::unique_ptr<TouchInfo> touch_info_;
 
+  // Current touch position reported by touchpad.
+  std::unique_ptr<TouchPoint> touch_point_;

[bshe, 2017/01/09 19:38:54]

Is it possible to use cur_touch_point_ directly to eliminate the need for
touch_point_?

[asimjour1, 2017/01/11 21:59:45]

It is possible. But more changes would be needed. 
prev_touch_point_ is updated only when the a new touch_point is reported or
extrapolation happens. Also, replacing the prev_touch_point_ with
cur_touch_point_ should be moved to the end of each controller update.

I'll make a bug and address this in another CL.

+
   // A pointer storing the touch point from previous frame.
   std::unique_ptr<TouchPoint> prev_touch_point_;
 
@@ -144,12 +149,18 @@ class VrController {
   // Overall velocity
   gvr::Vec2f overall_velocity_;
 
+  // Last velocity that is used for fling and direction detection
+  gvr::Vec2f last_velocity_;
+
   // Displacement of the touch point from the previews to the current touch
   gvr::Vec2f displacement_;
 
   int64_t last_touch_timestamp_ = 0;
   int64_t last_timestamp_nanos_ = 0;
 
+  // Number of consecutively extrapolated touch points
+  int extrapolated_touch_ = 0;
+
   DISALLOW_COPY_AND_ASSIGN(VrController);
 };