Fix controller positioning in VrShell when gyro reads are small

device/vr/vr_math.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "device/vr/vr_math.h"
 
 #include <cmath>
 
 #include "base/logging.h"
 
@@ skipping 102 matching lines @@
   float len = vec->Length();
   if (len == 0)
     return 0;
   vec->Scale(1.0f / len);
   return len;
 }
 
 void NormalizeQuat(Quatf* quat) {
   float len = sqrt(quat->qx * quat->qx + quat->qy * quat->qy +
                    quat->qz * quat->qz + quat->qw * quat->qw);
+  DCHECK_NE(len, 0);
+  if (len == 0)
+    return;
   quat->qx /= len;
   quat->qy /= len;
   quat->qz /= len;
   quat->qw /= len;
 }
 
 Quatf QuatFromAxisAngle(const RotationAxisAngle& axis_angle) {
   // Rotation angle is the product of |angle| and the magnitude of |axis|.
   gfx::Vector3dF normal(axis_angle.x, axis_angle.y, axis_angle.z);
   float length = NormalizeVector(&normal);
@@ skipping 147 matching lines @@
 
 float Clampf(float value, float min, float max) {
   if (value < min)
     return min;
   if (value > max)
     return max;
   return value;
 }
 
 }  // namespace vr