Fix controller positioning in VrShell when gyro reads are small

chrome/browser/android/vr_shell/elbow_model.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.
 
 // Adapted from:
 // https://github.com/googlevr/gvr-unity-sdk/blob/master/Samples/DaydreamLabsControllerPlayground/Assets/GoogleVR/Scripts/Controller/GvrArmModel.cs
 
 #include "chrome/browser/android/vr_shell/elbow_model.h"
 
 #include <cmath>
@@ skipping 14 matching lines @@
 constexpr gfx::Vector3dF kDefaultArmExtensionOffset = {-0.13f, 0.14f, -0.08f};
 constexpr float kMinExtensionAngle = 7.0f;
 constexpr float kMaxExtenstionAngle = 60.0f;
 constexpr float kExtensionWeight = 0.4f;
 constexpr float kDeltaAlpha = 3.0f;
 constexpr float kDefaultElbowRotationRatio = 0.4f;
 
 }  // namespace
 
 ElbowModel::ElbowModel(gvr::ControllerHandedness handedness)
-    : handedness_(handedness),
-      alpha_value_(1.0f),
-      torso_direction_{0.0f, 0.0f, 0.0f} {}
+    : handedness_(handedness), alpha_value_(1.0f), torso_direction_(kForward) {}
 
 ElbowModel::~ElbowModel() = default;
 
 void ElbowModel::UpdateHandedness() {
   handed_multiplier_ = {
       handedness_ == GVR_CONTROLLER_RIGHT_HANDED ? 1.0f : -1.0f, 1.0f, 1.0f};
   shoulder_rotation_ = kNoRotation;
   shoulder_position_ =
       vr::ScalePoint(kDefaultShoulderRight, handed_multiplier_);
 }
@@ skipping 85 matching lines @@
 void ElbowModel::UpdateTransparency(const UpdateData& update) {
   float distance_to_face = vr::ToVector(wrist_position_).Length();
   float alpha_change = kDeltaAlpha * update.delta_time_seconds;
   alpha_value_ = vr::Clampf(distance_to_face < kFadeDistanceFromFace
                                 ? alpha_value_ - alpha_change
                                 : alpha_value_ + alpha_change,
                             0.0f, 1.0f);
 }
 
 }  // namespace vr_shell