Remove frame flattening support as Chromium has no intention of using it

Source/WebCore/platform/ScrollView.cpp

Index: Source/WebCore/platform/ScrollView.cpp
diff --git a/Source/WebCore/platform/ScrollView.cpp b/Source/WebCore/platform/ScrollView.cpp
index 836f07127bd1260bce39107dde06d11993c4c555..b8b6524b77d636446958e0dccfe1211cfa8e7928 100644
--- a/Source/WebCore/platform/ScrollView.cpp
+++ b/Source/WebCore/platform/ScrollView.cpp
@@ -82,7 +82,7 @@ void ScrollView::removeChild(Widget* child)
 
 void ScrollView::setHasHorizontalScrollbar(bool hasBar)
 {
-    ASSERT(!hasBar || !avoidScrollbarCreation());
+    ASSERT(!hasBar);
     if (hasBar && !m_horizontalScrollbar) {
         m_horizontalScrollbar = createScrollbar(HorizontalScrollbar);
         addChild(m_horizontalScrollbar.get());
@@ -93,14 +93,14 @@ void ScrollView::setHasHorizontalScrollbar(bool hasBar)
         removeChild(m_horizontalScrollbar.get());
         m_horizontalScrollbar = 0;
     }
-    
+
     if (AXObjectCache* cache = axObjectCache())
         cache->handleScrollbarUpdate(this);
 }
 
 void ScrollView::setHasVerticalScrollbar(bool hasBar)
 {
-    ASSERT(!hasBar || !avoidScrollbarCreation());
+    ASSERT(!hasBar);
     if (hasBar && !m_verticalScrollbar) {
         m_verticalScrollbar = createScrollbar(VerticalScrollbar);
         addChild(m_verticalScrollbar.get());
@@ -425,13 +425,13 @@ void ScrollView::updateScrollbars(const IntSize& desiredOffset)
         newHasVerticalScrollbar = (vScroll == ScrollbarAlwaysOn);
 
     if (m_scrollbarsSuppressed || (hScroll != ScrollbarAuto && vScroll != ScrollbarAuto)) {
-        if (hasHorizontalScrollbar != newHasHorizontalScrollbar && (hasHorizontalScrollbar || !avoidScrollbarCreation()))
+        if (hasHorizontalScrollbar != newHasHorizontalScrollbar && hasHorizontalScrollbar)
             setHasHorizontalScrollbar(newHasHorizontalScrollbar);
-        if (hasVerticalScrollbar != newHasVerticalScrollbar && (hasVerticalScrollbar || !avoidScrollbarCreation()))
+        if (hasVerticalScrollbar != newHasVerticalScrollbar && hasVerticalScrollbar)
             setHasVerticalScrollbar(newHasVerticalScrollbar);
     } else {
         bool sendContentResizedNotification = false;
-        
+
         IntSize docSize = totalContentsSize();
         IntSize fullVisibleSize = visibleContentRect(IncludeScrollbars).size();
 
@@ -453,7 +453,7 @@ void ScrollView::updateScrollbars(const IntSize& desiredOffset)
         if (!newHasVerticalScrollbar && hasVerticalScrollbar && hScroll != ScrollbarAlwaysOn)
             newHasHorizontalScrollbar = false;
 
-        if (hasHorizontalScrollbar != newHasHorizontalScrollbar && (hasHorizontalScrollbar || !avoidScrollbarCreation())) {
+        if (hasHorizontalScrollbar != newHasHorizontalScrollbar && hasHorizontalScrollbar) {
             if (scrollOrigin().y() && !newHasHorizontalScrollbar)
                 ScrollableArea::setScrollOrigin(IntPoint(scrollOrigin().x(), scrollOrigin().y() - m_horizontalScrollbar->height()));
             if (m_horizontalScrollbar)
@@ -462,7 +462,7 @@ void ScrollView::updateScrollbars(const IntSize& desiredOffset)
             sendContentResizedNotification = true;
         }
 
-        if (hasVerticalScrollbar != newHasVerticalScrollbar && (hasVerticalScrollbar || !avoidScrollbarCreation())) {
+        if (hasVerticalScrollbar != newHasVerticalScrollbar && hasVerticalScrollbar) {
             if (scrollOrigin().x() && !newHasVerticalScrollbar)
                 ScrollableArea::setScrollOrigin(IntPoint(scrollOrigin().x() - m_verticalScrollbar->width(), scrollOrigin().y()));
             if (m_verticalScrollbar)