Chrome Version: ToT as of Dec 1, 4cc2259e5139 + custom patches
OS: Android

What steps will reproduce the problem?
(1) Open https://toji.github.io/webvr-samples/03-vr-presentation.html
(2) Enter VR
(3) Hit (back) button
(4) goto (2)

What is the expected result?
Enter and exit VR presentation as usual

What happens instead?
Chrome crashes:

signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0
     r0 00000000  r1 00000000  r2 3f000000  r3 00000000
     r4 ff965f00  r5 c3f62780  r6 c834dff0  r7 00000001
     r8 c1cb9749  r9 ff965fcc  sl 00000001  fp c1cb8e97
     ip c0abc401  sp ff965ed8  lr c1cb97d1  pc c2666b00

Stack Trace:
  RELADDR   FUNCTION                                                                                                                                                     FILE:LINE
  v------>  gvr::BufferViewport::SetSourceUv(gvr_rectf const&)                                                                                                           third_party/gvr-android-sdk/src/ndk/include/vr/gvr/capi/include/gvr.h:949
  01ea5b00  vr_shell::VrShell::UpdateWebVRTextureBounds(gvr_rectf const&, gvr_rectf const&)                                                                              chrome/browser/android/vr_shell/vr_shell.cc:1054
  014f87cf  device::GvrDevice::UpdateLayerBounds(mojo::InlinedStructPtr<device::mojom::VRLayerBounds>, mojo::InlinedStructPtr<device::mojom::VRLayerBounds>)             device/vr/android/gvr/gvr_device.cc:302
  014f7ee1  device::VRDisplayImpl::UpdateLayerBounds(mojo::InlinedStructPtr<device::mojom::VRLayerBounds>, mojo::InlinedStructPtr<device::mojom::VRLayerBounds>)         device/vr/vr_display_impl.cc:89
  014fa985  device::mojom::VRDisplayStubDispatch::Accept(device::mojom::VRDisplay*, mojo::internal::SerializationContext*, mojo::Message*) 

This happens ~0.1s after OnPresentChange and initializing the presenting delegate, presumably initialization is either incomplete or it's failing due to a race condition while updating.

See also  issue 670891  "WebVR dynamic-resolution sample page is not displayed correctly in presentation mode". Tying bounds to poses (frame index) instead of applying changes instantly should fix both.