Re-land^2 WebVR compositor bypass via BrowserMain context + mailbox

device/vr/vr_service.mojom

 // Copyright 2015 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.
 
 module device.mojom;
 
 import "mojo/common/time.mojom";
+import "gpu/ipc/common/mailbox.mojom";
+import "gpu/ipc/common/sync_token.mojom";
 
 // A field of view, given by 4 degrees describing the view from a center point.
 struct VRFieldOfView {
   float upDegrees;
   float downDegrees;
   float leftDegrees;
   float rightDegrees;
 };
 
 // A display's position, orientation, velocity, and acceleration state at the
 // given timestamp.
 struct VRPose {
   double timestamp;
   array<float, 4>? orientation;
   array<float, 3>? position;
   array<float, 3>? angularVelocity;
   array<float, 3>? linearVelocity;
   array<float, 3>? angularAcceleration;
   array<float, 3>? linearAcceleration;
+  int32 surfaceId;
+  int32 frameId;
+  gpu.mojom.Mailbox? mailbox;
+//  gpu.mojom.SyncToken syncToken;
 };
 
 struct VRDisplayCapabilities {
   bool hasOrientation;
   bool hasPosition;
   bool hasExternalDisplay;
   bool canPresent;
 };
 
 // Information about the optical properties for an eye in a VRDisplay.
@@ skipping 70 matching lines @@
 };
 
 interface VRDisplayClient {
   OnChanged(VRDisplayInfo display);
   OnExitPresent();
   OnBlur();
   OnFocus();
   OnActivate(VRDisplayEventReason reason);
   OnDeactivate(VRDisplayEventReason reason);
 };