Add more WebVR layout tests and fix small issues they found

third_party/WebKit/Source/modules/vr/VRDisplay.cpp

 // 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 "modules/vr/VRDisplay.h"
 
 #include "core/css/StylePropertySet.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/DocumentUserGestureToken.h"
 #include "core/dom/FrameRequestCallback.h"
@@ skipping 306 matching lines @@
   // A valid number of layers must be provided in order to present.
   if (layers.size() == 0 || layers.size() > m_capabilities->maxLayers()) {
     forceExitPresent();
     DOMException* exception =
         DOMException::create(InvalidStateError, "Invalid number of layers.");
     resolver->reject(exception);
     ReportPresentationResult(PresentationResult::InvalidNumberOfLayers);
     return promise;
   }
 
-  m_layer = layers[0];
-
-  if (!m_layer.source()) {
+  // If what we were given has an invalid source, need to exit fullscreen with
+  // previous, valid source, so delay m_layer reassignment
+  if (!layers[0].source()) {

[bsheedy, 2017/01/11 22:56:49]

Changed to address https://bugs.chromium.org/p/chromium/issues/detail?id=679952

     forceExitPresent();
     DOMException* exception =
         DOMException::create(InvalidStateError, "Invalid layer source.");
     resolver->reject(exception);
     ReportPresentationResult(PresentationResult::InvalidLayerSource);
     return promise;
   }
+  m_layer = layers[0];
 
   CanvasRenderingContext* renderingContext =
       m_layer.source()->renderingContext();
 
   if (!renderingContext || !renderingContext->is3d()) {
     forceExitPresent();
     DOMException* exception = DOMException::create(
         InvalidStateError, "Layer source must have a WebGLRenderingContext");
     resolver->reject(exception);
     ReportPresentationResult(
@@ skipping 421 matching lines @@
   visitor->trace(m_stageParameters);
   visitor->trace(m_eyeParametersLeft);
   visitor->trace(m_eyeParametersRight);
   visitor->trace(m_layer);
   visitor->trace(m_renderingContext);
   visitor->trace(m_scriptedAnimationController);
   visitor->trace(m_pendingPresentResolvers);
 }
 
 }  // namespace blink