Gracefully handle navigator.getVRDisplays() in detached contexts.

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

 // 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.
 
 #include "modules/vr/NavigatorVR.h"
 
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/Document.h"
 #include "core/dom/DocumentUserGestureToken.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/Fullscreen.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Navigator.h"
 #include "core/frame/UseCounter.h"
 #include "core/page/Page.h"
 #include "modules/vr/VRController.h"
 #include "modules/vr/VRDisplay.h"
 #include "modules/vr/VRGetDevicesCallback.h"
 #include "modules/vr/VRPose.h"
 #include "platform/UserGestureIndicator.h"
 #include "public/platform/Platform.h"
 #include "wtf/PtrUtil.h"
 
 namespace blink {
 
+namespace {
+
+void rejectNavigatorDetached(ScriptPromiseResolver* resolver) {
+  DOMException* exception = DOMException::create(
+      InvalidStateError, "The object is no longer associated with a document.");
+  resolver->reject(exception);
+}
+
+}  // namespace
+
 NavigatorVR* NavigatorVR::from(Document& document) {
   if (!document.frame() || !document.frame()->domWindow())
-    return 0;
+    return nullptr;
   Navigator& navigator = *document.frame()->domWindow()->navigator();
   return &from(navigator);
 }
 
 NavigatorVR& NavigatorVR::from(Navigator& navigator) {
   NavigatorVR* supplement = static_cast<NavigatorVR*>(
       Supplement<Navigator>::from(navigator, supplementName()));
   if (!supplement) {
     supplement = new NavigatorVR(navigator);
     provideTo(navigator, supplementName(), supplement);
   }
   return *supplement;
 }
 
 ScriptPromise NavigatorVR::getVRDisplays(ScriptState* scriptState,
                                          Navigator& navigator) {
+  if (!navigator.frame()) {
+    ScriptPromiseResolver* resolver =
+        ScriptPromiseResolver::create(scriptState);
+    ScriptPromise promise = resolver->promise();

[mthiesse, 2017/02/21 15:19:27]

nit: Why not remove this line, and return resolver->promise()?

[sof, 2017/02/21 15:29:12]

You have to call promise() before rejecting/resolving.

+    rejectNavigatorDetached(resolver);
+    return promise;
+  }
   return NavigatorVR::from(navigator).getVRDisplays(scriptState);
 }
 
 ScriptPromise NavigatorVR::getVRDisplays(ScriptState* scriptState) {
   ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
   ScriptPromise promise = resolver->promise();
 
   if (!document()) {
-    DOMException* exception = DOMException::create(
-        InvalidStateError, "The object is no longer associated to a document.");
-    resolver->reject(exception);
+    rejectNavigatorDetached(resolver);
     return promise;
   }
 
   UseCounter::count(*document(), UseCounter::VRGetDisplays);
   ExecutionContext* executionContext = scriptState->getExecutionContext();
   if (!executionContext->isSecureContext())
     UseCounter::count(*document(), UseCounter::VRGetDisplaysInsecureOrigin);
 
   Platform::current()->recordRapporURL("VR.WebVR.GetDisplays",
                                        document()->url());
 
   controller()->getDisplays(resolver);
 
   return promise;
 }
 
 VRController* NavigatorVR::controller() {
   if (!supplementable()->frame())
-    return 0;
+    return nullptr;
 
   if (!m_controller) {
     m_controller = new VRController(this);
     m_controller->setListeningForActivate(m_focused && m_listeningForActivate);
     m_controller->focusChanged();
   }
 
   return m_controller;
 }
 
 Document* NavigatorVR::document() {
-  return supplementable()->frame() ? supplementable()->frame()->document()
-                                   : nullptr;
+  if (!supplementable()->frame())
+    return nullptr;
+
+  return supplementable()->frame()->document();
 }
 
 DEFINE_TRACE(NavigatorVR) {
   visitor->trace(m_controller);
   Supplement<Navigator>::trace(visitor);
 }
 
 NavigatorVR::NavigatorVR(Navigator& navigator)
     : Supplement<Navigator>(navigator),
       FocusChangedObserver(navigator.frame()->page()) {
   navigator.frame()->domWindow()->registerEventListenerObserver(this);
   focusedFrameChanged();
 }
 
 NavigatorVR::~NavigatorVR() {}
 
 const char* NavigatorVR::supplementName() {
   return "NavigatorVR";
 }
 
 void NavigatorVR::enqueueVREvent(VRDisplayEvent* event) {
-  if (supplementable()->frame()) {
-    supplementable()->frame()->domWindow()->enqueueWindowEvent(event);
-  }
+  if (!supplementable()->frame())
+    return;
+
+  supplementable()->frame()->domWindow()->enqueueWindowEvent(event);
 }
 
 void NavigatorVR::dispatchVRGestureEvent(VRDisplayEvent* event) {
   if (!(supplementable()->frame()))
     return;
+
   UserGestureIndicator gestureIndicator(
       DocumentUserGestureToken::create(document()));
   LocalDOMWindow* window = supplementable()->frame()->domWindow();
   DCHECK(window);
   event->setTarget(window);
   window->dispatchEvent(event);
 }
 
 void NavigatorVR::focusedFrameChanged() {
   bool focused = isFrameFocused(supplementable()->frame());
@@ skipping 25 matching lines @@
 void NavigatorVR::didRemoveEventListener(LocalDOMWindow* window,
                                          const AtomicString& eventType) {
   if (eventType == EventTypeNames::vrdisplayactivate &&
       !window->hasEventListeners(EventTypeNames::vrdisplayactivate)) {
     m_listeningForActivate = false;
     controller()->setListeningForActivate(false);
   }
 }
 
 void NavigatorVR::didRemoveAllEventListeners(LocalDOMWindow* window) {
-  if (m_controller) {
-    m_controller->setListeningForActivate(false);
-    m_listeningForActivate = false;
-  }
+  if (!m_controller)
+    return;
+
+  m_controller->setListeningForActivate(false);
+  m_listeningForActivate = false;
 }
 
 }  // namespace blink