Skip drawing unsupported layers in forced software mode

cc/layers/scrollbar_layer_impl.cc

 // Copyright 2012 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 "cc/layers/scrollbar_layer_impl.h"
 
 #include "cc/animation/scrollbar_animation_controller.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/quad_sink.h"
 #include "cc/quads/solid_color_draw_quad.h"
@@ skipping 56 matching lines @@
 
   scrollbar_layer->set_thumb_thickness(thumb_thickness_);
   scrollbar_layer->set_thumb_length(thumb_length_);
   scrollbar_layer->set_track_start(track_start_);
   scrollbar_layer->set_track_length(track_length_);
 
   scrollbar_layer->set_track_resource_id(track_resource_id_);
   scrollbar_layer->set_thumb_resource_id(thumb_resource_id_);
 }
 
+bool ScrollbarLayerImpl::WillDraw(DrawMode draw_mode,
+                                  ResourceProvider* resource_provider) {
+  LayerImpl::WillDraw(draw_mode, resource_provider);

[danakj, 2013/06/04 15:30:44]

This call should only be made when returning true right? And it should early-out
before it when the return will be false?

+  return draw_mode != DRAW_MODE_RESOURCELESS_SOFTWARE ||
+         layer_tree_impl()->settings().solid_color_scrollbars;
+}
+
 void ScrollbarLayerImpl::AppendQuads(QuadSink* quad_sink,
                                      AppendQuadsData* append_quads_data) {
   bool premultipled_alpha = true;
   bool flipped = false;
   gfx::PointF uv_top_left(0.f, 0.f);
   gfx::PointF uv_bottom_right(1.f, 1.f);
   gfx::Rect bounds_rect(bounds());
   gfx::Rect content_bounds_rect(content_bounds());
 
   SharedQuadState* shared_quad_state =
@@ skipping 166 matching lines @@
 void ScrollbarLayerImpl::DidLoseOutputSurface() {
   track_resource_id_ = 0;
   thumb_resource_id_ = 0;
 }
 
 const char* ScrollbarLayerImpl::LayerTypeAsString() const {
   return "cc::ScrollbarLayerImpl";
 }
 
 }  // namespace cc