Fix WebVR does not properly stop presenting if requestPresent rejects.

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 233 matching lines @@
   if (!doc || !Fullscreen::fullscreenEnabled(*doc)) {
     DOMException* exception =
         DOMException::create(InvalidStateError, "Fullscreen is not enabled.");
     resolver->reject(exception);
     ReportPresentationResult(PresentationResult::FullscreenNotEnabled);
     return promise;
   }
 
   // A valid number of layers must be provided in order to present.
   if (layers.size() == 0 || layers.size() > m_capabilities->maxLayers()) {
-    forceExitPresent();
+    if (m_isPresenting) {

[mthiesse, 2017/02/13 15:33:34]

You should fix VRDisplay::forceExitPresent(), rather than fixing all of the
callsites.

[shaobo.yan, 2017/02/14 06:12:35]

Done.

+      if (m_display) {
+        m_display->ExitPresent();
+      } else {
+        forceExitPresent();
+      }
+    }
     DOMException* exception =
         DOMException::create(InvalidStateError, "Invalid number of layers.");
     resolver->reject(exception);
     ReportPresentationResult(PresentationResult::InvalidNumberOfLayers);
     return promise;
   }
 
   // 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()) {
-    forceExitPresent();
+    if (m_isPresenting) {
+      if (m_display) {
+        m_display->ExitPresent();
+      } else {
+        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();
+    if (m_isPresenting) {
+      if (m_display) {
+        m_display->ExitPresent();
+      } else {
+        forceExitPresent();
+      }
+    }
     DOMException* exception = DOMException::create(
         InvalidStateError, "Layer source must have a WebGLRenderingContext");
     resolver->reject(exception);
     ReportPresentationResult(
         PresentationResult::LayerSourceMissingWebGLContext);
     return promise;
   }
 
   // Save the WebGL script and underlying GL contexts for use by submitFrame().
   m_renderingContext = toWebGLRenderingContextBase(renderingContext);
   m_contextGL = m_renderingContext->contextGL();
 
   if ((m_layer.leftBounds().size() != 0 && m_layer.leftBounds().size() != 4) ||
       (m_layer.rightBounds().size() != 0 &&
        m_layer.rightBounds().size() != 4)) {
-    forceExitPresent();
+    if (m_isPresenting) {
+      if (m_display) {
+        m_display->ExitPresent();
+      } else {
+        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 (!m_pendingPresentResolvers.isEmpty()) {
     // If we are waiting on the results of a previous requestPresent call don't
@@ skipping 460 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