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 100 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 2844 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
+{
+    IntPoint max = ScrollView::maximumScrollPosition();
+    max.move(0, m_topControlsViewportAdjustment / visibleContentScaleFactor());

[leviw_travelin_and_unemployed, 2014/09/10 20:15:51]

Don't you want to ceil this value? If so, I'd expect a test that ensures we
don't lose a pixel.

[bokan, 2014/09/15 20:30:19]

I think we want to floor in this case (since we ceil the visibleSize, we should
floor anything we take away from it), but I'll admit this isn't terribly clear.
I've rewritten it to essentially the following:

max = contentHeight - ceil((visibleHeight-adjustment)/scale)

Which is what happens on the CC side. Also added to the test to check the
fractional pixel case.

+    return max;
+}
+
 } // namespace blink