Reset VisualViewport position after same page navigation

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All Rights Reserved.
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 418 matching lines @@
 
 void Page::didCommitLoad(LocalFrame* frame)
 {
     if (m_mainFrame == frame) {
         // TODO(rbyers): Most of this doesn't appear to take into account that each
         // SVGImage gets it's own Page instance.
         frameHost().consoleMessageStorage().clear();
         useCounter().didCommitLoad();
         deprecation().clearSuppression();
         frameHost().visualViewport().sendUMAMetrics();
+        // Need reset visual viewport position, fix for crbug.com/642279

[bokan, 2016/09/13 14:56:47]

Comments should answer "why?" not "what?". This comment just says what the line
below does (which we can easily see by looking at the line below). Instead, I'd
want to know *why* we reset the visual viewport here and not in a more logical
place. i.e. we need to reset the visual viewport position here since the setting
it earlier will clobber the current history item and didCommitLoad happens after
a new history item is created in FrameLoader.

+        frameHost().visualViewport().setScrollPosition(DoublePoint(), ProgrammaticScroll);
         m_hostsUsingFeatures.updateMeasurementsAndClear();
         UserGestureIndicator::clearProcessedUserGestureSinceLoad();
     }
 }
 
 void Page::acceptLanguagesChanged()
 {
     HeapVector<Member<LocalFrame>> frames;
 
     // Even though we don't fire an event from here, the LocalDOMWindow's will fire
@@ skipping 71 matching lines @@
 {
 }
 
 Page::PageClients::~PageClients()
 {
 }
 
 template class CORE_TEMPLATE_EXPORT Supplement<Page>;
 
 } // namespace blink