Add deprecation warnings to old powerful features on insecure origins.

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 186 matching lines @@
 {
     // NOTE: the context dispose phase is not supported in oilpan. Please
     // consider using the detach phase instead.
     m_fullScreenElement = nullptr;
     m_fullScreenElementStack.clear();
 }
 #endif
 
 void Fullscreen::requestFullscreen(Element& element, RequestType requestType)
 {
+    // It is required by isPrivilegedContext() but isn't
+    // actually used. This could be used later if a warning is shown in the

[philipj_slow, 2015/05/01 22:36:58]

The countDeprecation is the console warning, is there any chance that this
errorMessage will ever be used? Some other clients throw exceptions using this
message, but that will not make sense for the Fullscreen API. I think these
checks should be in fullscreenIsSupported, which is the place in the spec which
allows taking this into consideration. That would also ensure that
document.fullscreenEnabled is false if fullscreen will always fail, if it's made
to return false if (frame()->settings()->strictPowerfulFeatureRestrictions()).

[jww, 2015/05/05 21:29:53]

I think that's an accurate description of where it should be blocked in the long
term, but it appears to me to be the wrong place to measure usage. That is, I
don't think we don't want to measure that fullscreen is being used until
requestFullscreen is actually called.

[philipj_slow, 2015/05/06 07:43:55]

The fullscreen element ready check is only used in requestFullscreen() in both
spec and implementation. (I didn't check this when I commented, though, so your
skepticism is warranted.)

If you want to move this to the ready check I'll be happy to review, but there's
no hurry really.

+    // developer console.
+    String errorMessage;
+    if (document()->isPrivilegedContext(errorMessage))
+        UseCounter::count(document(), UseCounter::FullscreenSecureOrigin);
+    else
+        UseCounter::countDeprecation(document(), UseCounter::FullscreenInsecureOrigin);
+
     // Ignore this request if the document is not in a live frame.
     if (!document()->isActive())
         return;
 
     // If |element| is on top of |doc|'s fullscreen element stack, terminate these substeps.
     if (&element == fullscreenElement())
         return;
 
     do {
         // 1. If any of the following conditions are true, terminate these steps and queue a task to fire
@@ skipping 389 matching lines @@
 DEFINE_TRACE(Fullscreen)
 {
     visitor->trace(m_fullScreenElement);
     visitor->trace(m_fullScreenElementStack);
     visitor->trace(m_eventQueue);
     WillBeHeapSupplement<Document>::trace(visitor);
     DocumentLifecycleObserver::trace(visitor);
 }
 
 } // namespace blink