WebVR: Add sanity checks for decoded pose index values

chrome/browser/android/vr_shell/vr_shell.h

Index: chrome/browser/android/vr_shell/vr_shell.h
diff --git a/chrome/browser/android/vr_shell/vr_shell.h b/chrome/browser/android/vr_shell/vr_shell.h
index 819208f3a6a69719ffa68de93d0b3ab7ba85c498..7c01defe9071803c8dd6de65efdd0fdb2b49925f 100644
--- a/chrome/browser/android/vr_shell/vr_shell.h
+++ b/chrome/browser/android/vr_shell/vr_shell.h
@@ -133,6 +133,7 @@ class VrShell : public device::GvrDelegate, content::WebContentsObserver {
                     const std::vector<const ContentRectangle*>& elements);
   void DrawCursor(const gvr::Mat4f& render_matrix);
   void DrawWebVr();
+  bool WebVrPoseByteIsValid(int pose_index_byte);
 
   void UpdateController(const gvr::Vec3f& forward_vector);
   void SendEventsToTarget(VrInputManager* input_target,
@@ -205,6 +206,12 @@ class VrShell : public device::GvrDelegate, content::WebContentsObserver {
   // current backlog of poses which is 2-3 frames.
   static constexpr int kPoseRingBufferSize = 8;
   std::vector<gvr::Mat4f> webvr_head_pose_;
+  std::vector<bool> webvr_head_pose_valid_;
+  // Wait for a few seconds of valid poses before reprojecting, see
+  // crbug.com/667327. During this time, content is being drawn, just
+  // without reprojection.
+  static constexpr int webvr_min_valid_poses_ = 60;

[mthiesse, 2016/12/01 21:53:15]

I don't think we should land this min_valid_poses_ hack, unless you're convinced
that it really helps.

[klausw, 2016/12/01 22:36:04]

I've removed it, it's unclear. Got a black screen on try 21 with it removed just
now as opposed to try 67 with a 120 frame delay earlier, but that's not enough
data for good statistics.

+  int webvr_valid_poses_seen_ = 0;
   jint webvr_texture_id_ = 0;
 
   std::unique_ptr<VrController> controller_;