Adjust maximum scroll bounds on FrameView to account for top controls. (Blink-side)

Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
@@ skipping 289 matching lines @@
     // FIXME: This should probably be renamed as the 'inSubtreeLayout' parameter
     // passed around the FrameView layout methods can be true while this returns
     // false.
     bool isSubtreeLayout() const { return !!m_layoutSubtreeRoot; }
 
     // Sets the tickmarks for the FrameView, overriding the default behavior
     // which is to display the tickmarks corresponding to find results.
     // If |m_tickmarks| is empty, the default behavior is restored.
     void setTickmarks(const Vector<IntRect>& tickmarks) { m_tickmarks = tickmarks; }
 
+    // Since the compositor can resize the viewport due to top controls and
+    // commit scroll offsets before a WebView::resize occurs, we need to adjust
+    // our scroll extents to prevent clamping the scroll offsets.
+    void setTopControlsViewportAdjustment(float);
+
+    virtual IntPoint maximumScrollPosition() const OVERRIDE;
+
     // ScrollableArea interface
     virtual void invalidateScrollbarRect(Scrollbar*, const IntRect&) OVERRIDE;
     virtual void getTickmarks(Vector<IntRect>&) const OVERRIDE;
     virtual void scrollTo(const IntSize&) OVERRIDE;
     virtual IntRect scrollableAreaBoundingBox() const OVERRIDE;
     virtual bool scrollAnimatorEnabled() const OVERRIDE;
     virtual bool usesCompositedScrolling() const OVERRIDE;
     virtual GraphicsLayer* layerForScrolling() const OVERRIDE;
     virtual GraphicsLayer* layerForHorizontalScrollbar() const OVERRIDE;
     virtual GraphicsLayer* layerForVerticalScrollbar() const OVERRIDE;
@@ skipping 161 matching lines @@
     float m_inputEventsScaleFactorForEmulation;
 
     IntSize m_layoutSize;
     bool m_layoutSizeFixedToFrameSize;
 
     Timer<FrameView> m_didScrollTimer;
 
     Vector<IntRect> m_tickmarks;
 
     bool m_needsUpdateWidgetPositions;
+    float m_topControlsViewportAdjustment;
 };
 
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count)
 {
     if (m_isVisuallyNonEmpty)
         return;
     m_visuallyNonEmptyCharacterCount += count;
     // Use a threshold value to prevent very small amounts of visible content from triggering didFirstVisuallyNonEmptyLayout.
     // The first few hundred characters rarely contain the interesting content of the page.
     static const unsigned visualCharacterThreshold = 200;
@@ skipping 34 matching lines @@
         m_view->setCanInvalidatePaintDuringPerformLayout(m_originalValue);
     }
 private:
     FrameView* m_view;
     bool m_originalValue;
 };
 
 } // namespace blink
 
 #endif // FrameView_h