Attempt scroll restoration anytime viewport size changes

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 388 matching lines @@
 
     updateScrollableAreaSet();
 
     if (LayoutView* layoutView = this->layoutView()) {
         if (layoutView->usesCompositing())
             layoutView->compositor()->frameViewDidChangeSize();
     }
 
     viewportSizeChanged(newRect.width() != oldRect.width(), newRect.height() != oldRect.height());
 
-    if (oldRect.size() != newRect.size() && m_frame->isMainFrame())
-        page()->frameHost().visualViewport().mainFrameDidChangeSize();
+    if (oldRect.size() != newRect.size()) {
+        if (m_frame->isMainFrame())
+            page()->frameHost().visualViewport().mainFrameDidChangeSize();

[Nate Chapin, 2015/08/24 17:18:18]

Nit: this line should be m_frame->host() instead of page()->frameHost(). Would
you mind updating it while you're here?

[majidvp, 2015/08/25 19:12:42]

Done.

+        frame().loader().restoreScrollPositionAndViewState();
+    }
 }
 
 Page* FrameView::page() const
 {
     return frame().page();
 }
 
 LayoutView* FrameView::layoutView() const
 {
     return frame().contentLayoutObject();
@@ skipping 81 matching lines @@
     updateScrollbars(scrollOffsetDouble());
     ScrollableArea::contentsResized();
 
     Page* page = frame().page();
     if (!page)
         return;
 
     updateScrollableAreaSet();
 
     page->chromeClient().contentsSizeChanged(m_frame.get(), size);
-}
-
-IntPoint FrameView::clampOffsetAtScale(const IntPoint& offset, float scale) const
-{
-    IntPoint maxScrollExtent(contentsSize().width() - scrollOrigin().x(), contentsSize().height() - scrollOrigin().y());
-    FloatSize scaledSize = visibleContentSize();
-    if (scale)
-        scaledSize.scale(1 / scale);
-
-    IntPoint clampedOffset = offset;
-    clampedOffset = clampedOffset.shrunkTo(maxScrollExtent - expandedIntSize(scaledSize));
-    clampedOffset = clampedOffset.expandedTo(-scrollOrigin());
-
-    return clampedOffset;
+    frame().loader().restoreScrollPositionAndViewState();
 }
 
 void FrameView::adjustViewSize()
 {
     LayoutView* layoutView = this->layoutView();
     if (!layoutView)
         return;
 
     ASSERT(m_frame->view() == this);
 
@@ skipping 3442 matching lines @@
 
     if (!graphicsLayer)
         return;
 
     DeprecatedPaintLayer::mapRectToPaintInvalidationBacking(localFrame->contentLayoutObject(), paintInvalidationContainer, viewRect);
 
     graphicsLayerTimingRequests.add(graphicsLayer, Vector<std::pair<int64_t, WebRect>>()).storedValue->value.append(std::make_pair(m_frame->frameID(), enclosingIntRect(viewRect)));
 }
 
 } // namespace blink