Prevent repeated VRDisplay.requestPresent calls from spamming the device

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 347 matching lines @@
        m_layer.rightBounds().size() != 4)) {
     forceExitPresent();
     DOMException* exception = DOMException::create(
         InvalidStateError,
         "Layer bounds must either be an empty array or have 4 values");
     resolver->reject(exception);
     ReportPresentationResult(PresentationResult::InvalidLayerBounds);
     return promise;
   }
 
-  if (firstPresent) {
+  if (!m_pendingPresentResolvers.isEmpty()) {
+    // If we are waiting on the results of a previous requestPresent call don't
+    // fire a new request, just cache the resolver and resolve it when the
+    // original request returns.
+    m_pendingPresentResolvers.append(resolver);
+  } else if (firstPresent) {
     bool secureContext = scriptState->getExecutionContext()->isSecureContext();
     if (!m_display) {
       forceExitPresent();
       DOMException* exception = DOMException::create(
           InvalidStateError, "The service is no longer active.");
       resolver->reject(exception);
       return promise;
     }
-    m_display->RequestPresent(
-        secureContext, convertToBaseCallback(WTF::bind(
-                           &VRDisplay::onPresentComplete, wrapPersistent(this),
-                           wrapPersistent(resolver))));
+
+    m_pendingPresentResolvers.append(resolver);
+    m_display->RequestPresent(secureContext, convertToBaseCallback(WTF::bind(
+                                                 &VRDisplay::onPresentComplete,
+                                                 wrapPersistent(this))));
   } else {
     updateLayerBounds();
     resolver->resolve();
     ReportPresentationResult(PresentationResult::SuccessAlreadyPresenting);
   }
 
   return promise;
 }
 
-void VRDisplay::onPresentComplete(ScriptPromiseResolver* resolver,
-                                  bool success) {
+void VRDisplay::onPresentComplete(bool success) {
   if (success) {
-    this->beginPresent(resolver);
+    this->beginPresent();
   } else {
     this->forceExitPresent();
     DOMException* exception = DOMException::create(
         NotAllowedError, "Presentation request was denied.");
-    resolver->reject(exception);
+
+    while (!m_pendingPresentResolvers.isEmpty()) {
+      ScriptPromiseResolver* resolver = m_pendingPresentResolvers.takeFirst();
+      resolver->reject(exception);
+    }
   }
 }
 
 ScriptPromise VRDisplay::exitPresent(ScriptState* scriptState) {
   ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
   ScriptPromise promise = resolver->promise();
 
   if (!m_isPresenting) {
     // Can't stop presenting if we're not presenting.
     DOMException* exception =
@@ skipping 10 matching lines @@
   }
   m_display->ExitPresent();
 
   resolver->resolve();
 
   forceExitPresent();
 
   return promise;
 }
 
-void VRDisplay::beginPresent(ScriptPromiseResolver* resolver) {
+void VRDisplay::beginPresent() {
   Document* doc = m_navigatorVR->document();
   std::unique_ptr<UserGestureIndicator> gestureIndicator;
   if (m_capabilities->hasExternalDisplay()) {
     forceExitPresent();
     DOMException* exception = DOMException::create(
         InvalidStateError,
         "VR Presentation not implemented for this VRDisplay.");
-    resolver->reject(exception);
+    while (!m_pendingPresentResolvers.isEmpty()) {
+      ScriptPromiseResolver* resolver = m_pendingPresentResolvers.takeFirst();
+      resolver->reject(exception);
+    }
     ReportPresentationResult(
         PresentationResult::PresentationNotSupportedByDisplay);
     return;
   } else {
     // TODO(klausw,crbug.com/655722): Need a proper VR compositor, but
     // for the moment on mobile we'll just make the canvas fullscreen
     // so that VrShell can pick it up through the standard (high
     // latency) compositing path.
     auto canvas = m_layer.source();
     auto inlineStyle = canvas->inlineStyle();
@@ skipping 38 matching lines @@
   if (doc) {
     Platform::current()->recordRapporURL("VR.WebVR.PresentSuccess",
                                          WebURL(doc->url()));
   }
 
   m_isPresenting = true;
   ReportPresentationResult(PresentationResult::Success);
 
   updateLayerBounds();
 
-  resolver->resolve();
+  while (!m_pendingPresentResolvers.isEmpty()) {
+    ScriptPromiseResolver* resolver = m_pendingPresentResolvers.takeFirst();
+    resolver->resolve();
+  }
   OnPresentChange();
 }
 
 void VRDisplay::forceExitPresent() {
   if (m_isPresenting) {
     if (!m_capabilities->hasExternalDisplay()) {
       auto canvas = m_layer.source();
       Fullscreen::fullyExitFullscreen(canvas->document());
       m_fullscreenCheckTimer.stop();
       if (!m_fullscreenOrigWidth.isNull()) {
@@ skipping 221 matching lines @@
 
 DEFINE_TRACE(VRDisplay) {
   visitor->trace(m_navigatorVR);
   visitor->trace(m_capabilities);
   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