Allow objects without scrollbars to be scrollable

Source/core/rendering/RenderListBox.cpp

Index: Source/core/rendering/RenderListBox.cpp
diff --git a/Source/core/rendering/RenderListBox.cpp b/Source/core/rendering/RenderListBox.cpp
index 6ebf5ef11adc88b1d929470a72ab6eb3e649c998..ca7b6c69207da6b8806882f6bc5ffef28b2e0799 100644
--- a/Source/core/rendering/RenderListBox.cpp
+++ b/Source/core/rendering/RenderListBox.cpp
@@ -176,7 +176,6 @@ void RenderListBox::layout()
     if (m_vBar) {
         bool enabled = numVisibleItems() < numItems();
         m_vBar->setEnabled(enabled);
-        m_vBar->setSteps(1, max(1, numVisibleItems() - 1), itemHeight());
         m_vBar->setProportion(numVisibleItems(), numItems());
         if (!enabled) {
             scrollToOffsetWithoutAnimation(VerticalScrollbar, 0);
@@ -624,7 +623,7 @@ void RenderListBox::valueChanged(unsigned listIndex)
 
 int RenderListBox::scrollSize(ScrollbarOrientation orientation) const
 {
-    return ((orientation == VerticalScrollbar) && m_vBar) ? (m_vBar->totalSize() - m_vBar->visibleSize()) : 0;
+    return orientation == VerticalScrollbar ? (numItems() - numVisibleItems()) : 0;
 }
 
 int RenderListBox::scrollPosition(Scrollbar*) const
@@ -632,6 +631,13 @@ int RenderListBox::scrollPosition(Scrollbar*) const
     return m_indexOffset;
 }
 
+IntPoint RenderListBox::scrollPosition() const
+{
+    int x = 0;
+    int y = m_indexOffset;
+    return IntPoint(x, y);

[aelias_OOO_until_Jul13, 2013/06/19 22:25:12]

nit: return IntPoint(0, m_indexOffset);

[bokan, 2013/06/19 23:50:58]

Done.

+}
+
 void RenderListBox::setScrollOffset(const IntPoint& offset)
 {
     scrollTo(offset.y());
@@ -839,6 +845,26 @@ IntPoint RenderListBox::maximumScrollPosition() const
     return IntPoint(0, numItems() - numVisibleItems());
 }
 
+bool RenderListBox::userInputScrollable(ScrollbarOrientation orientation) const
+{
+    return orientation == VerticalScrollbar;
+}
+
+int RenderListBox::lineStep(ScrollbarOrientation) const
+{
+    return 1;
+}
+
+int RenderListBox::pageStep(ScrollbarOrientation orientation) const
+{
+    return max(1, numVisibleItems() - 1);
+}
+
+float RenderListBox::pixelStep(ScrollbarOrientation) const
+{
+    return 1.0f / itemHeight();
+}
+
 ScrollableArea* RenderListBox::enclosingScrollableArea() const
 {
     // FIXME: Return a RenderLayer that's scrollable.