Provide WebVR pose data only to the focused frame.

third_party/WebKit/Source/core/page/FocusController.cpp

 /*
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nuanti Ltd.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 37 matching lines @@
 #include "core/frame/RemoteFrame.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLAreaElement.h"
 #include "core/html/HTMLImageElement.h"
 #include "core/html/HTMLPlugInElement.h"
 #include "core/html/HTMLShadowElement.h"
 #include "core/html/HTMLSlotElement.h"
 #include "core/html/TextControlElement.h"
 #include "core/input/EventHandler.h"
 #include "core/page/ChromeClient.h"
+#include "core/page/FocusChangedObserver.h"
 #include "core/page/FrameTree.h"
 #include "core/page/Page.h"
 #include "core/layout/HitTestResult.h"
 #include "core/page/SpatialNavigation.h"
 #include <limits>
 
 namespace blink {
 
 using namespace HTMLNames;
 
@@ skipping 691 matching lines @@
     newFrame->selection().setFocused(true);
     newFrame->domWindow()->dispatchEvent(Event::create(EventTypeNames::focus));
   }
 
   m_isChangingFocusedFrame = false;
 
   // Checking client() is necessary, as the frame might have been detached as
   // part of dispatching the focus event above. See https://crbug.com/570874.
   if (m_focusedFrame && m_focusedFrame->client() && notifyEmbedder)
     m_focusedFrame->client()->frameFocused();
+
+  notifyFocusChangedObservers();
 }
 
 void FocusController::focusDocumentView(Frame* frame, bool notifyEmbedder) {
   DCHECK(!frame || frame->page() == m_page);
   if (m_focusedFrame == frame)
     return;
 
   LocalFrame* focusedFrame = (m_focusedFrame && m_focusedFrame->isLocalFrame())
                                  ? toLocalFrame(m_focusedFrame.get())
                                  : nullptr;
@@ skipping 82 matching lines @@
     setFocusedFrame(m_page->mainFrame());
 
   // setFocusedFrame above might reject to update m_focusedFrame, or
   // m_focusedFrame might be changed by blur/focus event handlers.
   if (m_focusedFrame && m_focusedFrame->isLocalFrame() &&
       toLocalFrame(m_focusedFrame.get())->view()) {
     toLocalFrame(m_focusedFrame.get())->selection().setFocused(focused);
     dispatchEventsOnWindowAndFocusedElement(
         toLocalFrame(m_focusedFrame.get())->document(), focused);
   }
+
+  notifyFocusChangedObservers();

[jbroman, 2017/02/02 16:07:20]

Won't this possibly notify twice, since setFocusedFrame also does so?

[mthiesse, 2017/02/02 17:52:18]

Yes, intentionally. We need to call it in setFocusedFrame, because that's called
from a bunch of places, but setFocused also changes whether or not the "Focused
Frame" is actually focused, even if it doesn't change the "Focused Frame". I
didn't want to check from setFocused whether or not setFocusedFrame would be
called, whether it would return early, etc. to avoid notifying twice.

I could separate this into two callbacks, observer->focusedFrameChanged and
observer->focusChanged if that helps?

 }
 
 bool FocusController::setInitialFocus(WebFocusType type) {
   bool didAdvanceFocus = advanceFocus(type, true);
 
   // If focus is being set initially, accessibility needs to be informed that
   // system focus has moved into the web area again, even if focus did not
   // change within WebCore.  PostNotification is called instead of
   // handleFocusedUIElementChanged, because this will send the notification even
   // if the element is the same.
@@ skipping 508 matching lines @@
         nodeRectInAbsoluteCoordinates(container, true /* ignore border */);
     container =
         scrollableEnclosingBoxOrParentFrameForNodeInDirection(type, container);
     if (container && container->isDocumentNode())
       toDocument(container)->updateStyleAndLayoutIgnorePendingStylesheets();
   } while (!consumed && container);
 
   return consumed;
 }
 
+void FocusController::registerFocusChangedObserver(
+    FocusChangedObserver* observer) {
+  DCHECK(observer);
+  DCHECK(!m_focusChangedObservers.contains(observer));
+  m_focusChangedObservers.insert(observer);
+}
+
+void FocusController::notifyFocusChangedObservers() const {
+  for (auto& it : m_focusChangedObservers) {

[jbroman, 2017/02/02 16:07:20]

nit: const auto&

[mthiesse, 2017/02/02 17:52:18]

Done.

+    it->focusedFrameChanged();
+  }

[jbroman, 2017/02/02 16:07:20]

super-nit: don't need the braces

[mthiesse, 2017/02/02 17:52:18]

Done.

+}
+
 DEFINE_TRACE(FocusController) {
   visitor->trace(m_page);
   visitor->trace(m_focusedFrame);
+  visitor->trace(m_focusChangedObservers);
 }
 
 }  // namespace blink