Cleanup viewport scrolling for future scroll customization work.

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/gpu/render_widget_compositor.h"
 
 #include <limits>
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 425 matching lines @@
   // Webview does not own the surface so should not clear it.
   settings.renderer_settings.should_clear_root_render_pass =
       !synchronous_compositor_factory;
 
   // TODO(danakj): Only do this on low end devices.
   settings.create_low_res_tiling = true;
 
   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);
   } else {
     settings.scrollbar_animator = cc::LayerTreeSettings::LINEAR_FADE;
     settings.solid_color_scrollbar_color = SkColorSetARGB(128, 128, 128, 128);
   }
   settings.scrollbar_fade_delay_ms = 500;
   settings.scrollbar_fade_resize_delay_ms = 500;
   settings.scrollbar_fade_duration_ms = 300;
@@ skipping 571 matching lines @@
     return;
   provider->ContextGL()->RateLimitOffscreenContextCHROMIUM();
 }
 
 void RenderWidgetCompositor::SetSurfaceIdNamespace(
     uint32_t surface_id_namespace) {
   layer_tree_host_->set_surface_id_namespace(surface_id_namespace);
 }
 
 }  // namespace content