Get rid of clampScrollOffset and make maximumScrollPosition sane.

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 2972 matching lines @@
 
 void FrameView::setTopControlsViewportAdjustment(float adjustment)
 {
     m_topControlsViewportAdjustment = adjustment;
 }
 
 IntPoint FrameView::maximumScrollPosition() const
 {
     // Make the same calculation as in CC's LayerImpl::MaxScrollOffset()
     // FIXME: We probably shouldn't be storing the bounds in a float. crbug.com/422331.
-    FloatSize visibleSize = visibleContentSize(ExcludeScrollbars);
-    visibleSize.expand(0, m_topControlsViewportAdjustment);
-
-    FloatSize contentBounds = contentsSize();
-    contentBounds = flooredIntSize(contentBounds);
-
-    FloatSize maximumOffset = contentBounds - visibleSize - toIntSize(scrollOrigin());
-
-    IntPoint snappedMaximumOffset = flooredIntPoint(maximumOffset);
-    snappedMaximumOffset = snappedMaximumOffset.expandedTo(minimumScrollPosition());
-    return snappedMaximumOffset;
+    IntSize visibleSize = visibleContentSize(ExcludeScrollbars) + topControlsSize();
+    IntSize contentBounds = contentsSize();
+    IntPoint maximumPosition = -scrollOrigin() + (contentBounds - visibleSize);
+    return maximumPosition.expandedTo(minimumScrollPosition());
 }
 
 void FrameView::addChild(PassRefPtrWillBeRawPtr<Widget> prpChild)
 {
     Widget* child = prpChild.get();
     ASSERT(child != this && !child->parent());
     child->setParent(this);
     m_children.add(prpChild);
 }
 
@@ skipping 927 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