Replace pinch scrollbars with regular scrollbars.

Source/core/frame/FrameView.cpp

Index: Source/core/frame/FrameView.cpp
diff --git a/Source/core/frame/FrameView.cpp b/Source/core/frame/FrameView.cpp
index feffce69b9fc3057ce92d0ef13c11897d32aa012..704530f2b7b1dea3924434ccc600b7874f904358 100644
--- a/Source/core/frame/FrameView.cpp
+++ b/Source/core/frame/FrameView.cpp
@@ -676,6 +676,13 @@ bool FrameView::usesCompositedScrolling() const
     return false;
 }
 
+GraphicsLayer* FrameView::layerForScrollbarContainer() const

[skobes, 2015/08/25 00:19:01]

Do we need a similar override in DeprecatedPaintLayerScrollableArea when
--root-layer-scrolls is enabled?

[aelias_OOO_until_Jul13, 2015/08/25 02:50:27]

Done, and I also fixed the layer attachment with that flag.

+{
+    if (m_frame->isMainFrame())
+        return page()->frameHost().visualViewport().layerForScrollbarContainer();
+    return layerForContainer();
+}
+
 GraphicsLayer* FrameView::layerForScrolling() const
 {
     LayoutView* layoutView = this->layoutView();
@@ -2957,11 +2964,6 @@ bool FrameView::isFlippedDocument() const
     return layoutView->hasFlippedBlocksWritingMode();
 }
 
-bool FrameView::visualViewportSuppliesScrollbars() const
-{
-    return m_frame->isMainFrame() && m_frame->settings() && m_frame->settings()->viewportMetaEnabled();
-}
-
 AXObjectCache* FrameView::axObjectCache() const
 {
     if (frame().document())
@@ -3209,7 +3211,6 @@ void FrameView::windowResizerRectChanged()
 
 bool FrameView::hasOverlayScrollbars() const
 {
-
     return (m_horizontalScrollbar && m_horizontalScrollbar->isOverlayScrollbar())
         || (m_verticalScrollbar && m_verticalScrollbar->isOverlayScrollbar());
 }
@@ -3241,8 +3242,11 @@ void FrameView::computeScrollbarExistence(bool& newHasHorizontalScrollbar, bool&
     if (vScroll == ScrollbarAuto)
         newHasVerticalScrollbar = docSize.height() > visibleHeight();
 
-    if (hasOverlayScrollbars())
+    if (hasOverlayScrollbars()) {
+        if (m_frame->isMainFrame())
+            newHasHorizontalScrollbar = newHasVerticalScrollbar = true;

[skobes, 2015/08/25 00:19:01]

Why is this needed?

[aelias_OOO_until_Jul13, 2015/08/25 02:50:27]

So that scrollbars are shown when zooming in (particularly on Android), even if
they weren't needed at minimum scale.  Note that CC is smart about hiding a
scrollbar if that orientation is nonscrollable.

[aelias_OOO_until_Jul13, 2015/08/26 04:47:48]

Unfortunately, this approach turned out to be flaky (and broken in a different
way when --root-layer-scrolls), so I deleted this line and ended up bringing
back the VisualViewport scrollbars, which are now Android-only scrollbars.  The
VisualViewport scrollbar deletion should be more feasible when
--root-layer-scrolls is shipped.

         return;
+    }
 
     IntSize fullVisibleSize = visibleContentRect(IncludeScrollbars).size();
 
@@ -3383,14 +3387,6 @@ bool FrameView::shouldIgnoreOverflowHidden() const
 
 void FrameView::updateScrollbars(const DoubleSize& desiredOffset)
 {
-    // Avoid drawing two sets of scrollbars when visual viewport is enabled.
-    if (visualViewportSuppliesScrollbars()) {
-        setHasHorizontalScrollbar(false);
-        setHasVerticalScrollbar(false);
-        setScrollOffsetFromUpdateScrollbars(desiredOffset);
-        return;
-    }
-
     if (m_inUpdateScrollbars)
         return;
     InUpdateScrollbarsScope inUpdateScrollbarsScope(this);