Clean up WebVR RequestPresent and make callback asynchronous.

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

Index: third_party/WebKit/Source/modules/vr/VRDisplay.cpp
diff --git a/third_party/WebKit/Source/modules/vr/VRDisplay.cpp b/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
index 5095591ba779b8a8d11fd83c476028c02176f23f..670c4013f8ec4132eb7b11f0ef26f6ee71ed6cec 100644
--- a/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
+++ b/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
@@ -5,6 +5,7 @@
 #include "modules/vr/VRDisplay.h"
 
 #include "core/dom/DOMException.h"
+#include "core/dom/DocumentUserGestureToken.h"
 #include "core/dom/FrameRequestCallback.h"
 #include "core/dom/Fullscreen.h"
 #include "core/dom/ScriptedAnimationController.h"
@@ -335,18 +336,6 @@ ScriptPromise VRDisplay::requestPresent(ScriptState* scriptState,
     return promise;
   }
 
-  if (!m_capabilities->hasExternalDisplay()) {
-    // TODO: 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.
-    Fullscreen::requestFullscreen(*m_layer.source(),
-                                  Fullscreen::UnprefixedRequest);
-
-    // Check to see if the canvas is still the current fullscreen
-    // element once per second.
-    m_fullscreenCheckTimer.startRepeating(1.0, BLINK_FROM_HERE);
-  }
-
   if (firstPresent) {
     bool secureContext = scriptState->getExecutionContext()->isSecureContext();
     if (!m_display) {
@@ -409,6 +398,8 @@ ScriptPromise VRDisplay::exitPresent(ScriptState* scriptState) {
 }
 
 void VRDisplay::beginPresent(ScriptPromiseResolver* resolver) {
+  Document* doc = m_navigatorVR->document();
+  std::unique_ptr<UserGestureIndicator> gestureIndicator;
   if (m_capabilities->hasExternalDisplay()) {
     forceExitPresent();
     DOMException* exception = DOMException::create(
@@ -418,9 +409,25 @@ void VRDisplay::beginPresent(ScriptPromiseResolver* resolver) {
     ReportPresentationResult(
         PresentationResult::PresentationNotSupportedByDisplay);
     return;
+  } else {
+    // TODO: 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.
+    if (doc) {
+      // Since the callback for requestPresent is asynchronous, we've lost our
+      // UserGestureToken, and need to create a new one to enter fullscreen.
+      gestureIndicator =
+          wrapUnique(new UserGestureIndicator(DocumentUserGestureToken::create(
+              doc, UserGestureToken::Status::PossiblyExistingGesture)));
+    }
+    Fullscreen::requestFullscreen(*m_layer.source(),
+                                  Fullscreen::UnprefixedRequest);
+
+    // Check to see if the canvas is still the current fullscreen
+    // element once per second.
+    m_fullscreenCheckTimer.startRepeating(1.0, BLINK_FROM_HERE);
   }
 
-  Document* doc = m_navigatorVR->document();
   if (doc) {
     Platform::current()->recordRapporURL("VR.WebVR.PresentSuccess",
                                          WebURL(doc->url()));