Cleanup viewport scrolling for future scroll customization work.

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index f0a15aaed9fc15c1146157b50a13ffb022b82ea3..1b12927c4f7c8ce4ec5f23424e94ece0702295c5 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -443,6 +443,8 @@ void RenderWidgetCompositor::Initialize() {
   settings.use_external_begin_frame_source = true;
 
 #elif !defined(OS_MACOSX)
+  settings.report_overscroll_only_for_scrollable_axes = false;

[tdresser, 2015/07/06 15:22:44]

This value was previously set incorrectly for aura. We rely on overscroll
information for gesture navigation, which needs to take place regardless of
whether or not an axis is scrollable.

Without this change WebContentsViewAuraTest.VerticalOverscroll fails.

+
   if (ui::IsOverlayScrollbarEnabled()) {
     settings.scrollbar_animator = cc::LayerTreeSettings::THINNING;
     settings.solid_color_scrollbar_color = SkColorSetARGB(128, 128, 128, 128);