WebVR: fix angular velocity calculation for headset

device/vr/android/gvr/gvr_delegate.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/android/gvr/gvr_delegate.h"
 
 #include "base/trace_event/trace_event.h"
 #include "third_party/gvr-android-sdk/src/libraries/headers/vr/gvr/capi/include/gvr.h"
 #include "third_party/gvr-android-sdk/src/libraries/headers/vr/gvr/capi/include/gvr_types.h"
 #include "ui/gfx/geometry/vector3d_f.h"
@@ skipping 48 matching lines @@
 
   gfx::Transform delta_mat;
   gfx::Transform inverse_head_mat;
   // Calculate difference matrix, and inverse head matrix rotation.
   // For the inverse rotation, just transpose the 3x3 subsection.
   //
   // Assume that epsilon is nonzero since it's based on a compile-time constant
   // provided by the caller.
   for (int j = 0; j < 3; ++j) {
     for (int i = 0; i < 3; ++i) {
-      delta_mat.matrix().set(j, i,
-                             head_mat_2.matrix().get(j, i) -
-                                 head_mat.matrix().get(j, i) / epsilon_seconds);
+      delta_mat.matrix().set(
+          j, i,
+          (head_mat_2.matrix().get(j, i) - head_mat.matrix().get(j, i)) /
+              epsilon_seconds);
       inverse_head_mat.matrix().set(j, i, head_mat.matrix().get(i, j));
     }
     delta_mat.matrix().set(j, 3, 0);
     delta_mat.matrix().set(3, j, 0);
     inverse_head_mat.matrix().set(j, 3, 0);
     inverse_head_mat.matrix().set(3, j, 0);
   }
   delta_mat.matrix().set(3, 3, 1);
   inverse_head_mat.matrix().set(3, 3, 1);
   gfx::Transform omega_mat = delta_mat * inverse_head_mat;
@@ skipping 183 matching lines @@
     gvr::Mat4f eye_mat = gvr_api->GetEyeFromHeadMatrix(eye);
     eye_params->offset[0] = -eye_mat.m[0][3];
     eye_params->offset[1] = -eye_mat.m[1][3];
     eye_params->offset[2] = -eye_mat.m[2][3];
   }
 
   return device;
 }
 
 }  // namespace device