Allow going fullscreen during a screen orientation change handler.

third_party/WebKit/Source/core/dom/Fullscreen.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
@@ skipping 28 matching lines @@
 #include "core/frame/Settings.h"
 #include "core/frame/UseCounter.h"
 #include "core/html/HTMLIFrameElement.h"
 #include "core/html/HTMLMediaElement.h"
 #include "core/input/EventHandler.h"
 #include "core/inspector/ConsoleMessage.h"
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/layout/LayoutFullScreen.h"
 #include "core/layout/api/LayoutFullScreenItem.h"
 #include "core/page/ChromeClient.h"
+#include "platform/ScopedOrientationChangeIndicator.h"
 #include "platform/UserGestureIndicator.h"
 
 namespace blink {
 
 using namespace HTMLNames;
 
 namespace {
 
 bool fullscreenIsAllowedForAllOwners(const Document& document)
 {
@@ skipping 188 matching lines @@
 
     do {
         // 1. If any of the following conditions are true, terminate these steps and queue a task to fire
         // an event named fullscreenerror with its bubbles attribute set to true on the context object's
         // node document:
 
         // The fullscreen element ready check returns false.
         if (!fullscreenElementReady(element))
             break;
 
-        // This algorithm is not allowed to show a pop-up:
-        //   An algorithm is allowed to show a pop-up if, in the task in which the algorithm is running, either:
-        //   - an activation behavior is currently being processed whose click event was trusted, or
-        //   - the event listener for a trusted click event is being handled.
+        // Fullscreen is not supported.
+        if (!fullscreenIsSupported(element.document()))
+            break;
+
+        // This algorithm is not allowed to request fullscreen.
+        // An algorithm is allowed to request fullscreen if one of the following
+        // is true:
+        //  - the algorithm is triggered by a user activation.
+        //  - the algorithm is triggered by a user generated orientation change.
         //
         // If |forCrossProcessDescendant| is true, requestFullscreen
         // was already called on a descendant element in another process, and
         // getting here means that it already passed the user gesture check.
-        if (!UserGestureIndicator::utilizeUserGesture() && !forCrossProcessDescendant) {
+        if (!UserGestureIndicator::utilizeUserGesture() && !ScopedOrientationChangeIndicator::processingOrientationChange() && !forCrossProcessDescendant) {
             String message = ExceptionMessages::failedToExecute("requestFullScreen",
                 "Element", "API can only be initiated by a user gesture.");
             document()->addConsoleMessage(
                 ConsoleMessage::create(JSMessageSource, WarningMessageLevel, message));
             break;
         }
 
-        // Fullscreen is not supported.
-        if (!fullscreenIsSupported(element.document()))

[foolip, 2016/07/23 00:33:54]

Why was this block moved up?

-            break;
-
         // 2. Let doc be element's node document. (i.e. "this")
         Document* currentDoc = document();
 
         // 3. Let docs be all doc's ancestor browsing context's documents (if any) and doc.
         //
         // For OOPIF scenarios, |docs| will only contain documents for local
         // ancestors, and remote ancestors will be processed in their
         // respective processes.  This preserves the spec's event firing order
         // for local ancestors, but not for remote ancestors.  However, that
         // difference shouldn't be observable in practice: a fullscreenchange
@@ skipping 405 matching lines @@
 DEFINE_TRACE(Fullscreen)
 {
     visitor->trace(m_fullScreenElement);
     visitor->trace(m_fullScreenElementStack);
     visitor->trace(m_eventQueue);
     Supplement<Document>::trace(visitor);
     ContextLifecycleObserver::trace(visitor);
 }
 
 } // namespace blink