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

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 103 matching lines @@
     , m_wasScrolledByUser(false)
     , m_inProgrammaticScroll(false)
     , m_safeToPropagateScrollToParent(true)
     , m_isTrackingPaintInvalidations(false)
     , m_scrollCorner(nullptr)
     , m_visibleContentScaleFactor(1)
     , m_inputEventsScaleFactorForEmulation(1)
     , m_layoutSizeFixedToFrameSize(true)
     , m_didScrollTimer(this, &FrameView::didScrollTimerFired)
     , m_needsUpdateWidgetPositions(false)
+    , m_topControlsViewportAdjustment(0)
 {
     ASSERT(m_frame);
     init();
 
     if (!m_frame->isMainFrame())
         return;
 
     ScrollableArea::setVerticalScrollElasticity(ScrollElasticityAllowed);
     ScrollableArea::setHorizontalScrollElasticity(ScrollElasticityAllowed);
 }
@@ skipping 2867 matching lines @@
 
 void FrameView::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
 {
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
     if (AXObjectCache* cache = axObjectCache()) {
         cache->remove(scrollbar);
         cache->handleScrollbarUpdate(this);
     }
 }
 
+void FrameView::setTopControlsViewportAdjustment(float adjustment)
+{
+    m_topControlsViewportAdjustment = adjustment;
+}
+
+IntPoint FrameView::maximumScrollPosition() const
+{
+    FloatSize visibleContentSizeF = unscaledVisibleContentSize(ExcludeScrollbars);
+    visibleContentSizeF.expand(0, -m_topControlsViewportAdjustment);
+    visibleContentSizeF.scale(1 / visibleContentScaleFactor());
+    IntSize visibleSize = expandedIntSize(visibleContentSizeF);
+
+    IntPoint maximumOffset(
+        contentsWidth() - visibleSize.width() - scrollOrigin().x(),
+        contentsHeight() - visibleSize.height() - scrollOrigin().y());
+    maximumOffset.clampNegativeToZero();
+    return maximumOffset;
+}
+
 } // namespace blink