Add flag for drawing layers to screen with Ganesh

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index f3e99e23dbc1f4848bbf3a0d27a1e9949f537af9..8402298a03e19a680e6e08729996d06d9a71a74b 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -99,7 +99,10 @@ void PictureLayerImpl::AppendQuads(QuadSink* quad_sink,
       quad_sink->UseSharedQuadState(CreateSharedQuadState());
   AppendDebugBorderQuad(quad_sink, shared_quad_state, append_quads_data);
 
-  if (!append_quads_data->allow_tile_draw_quads) {
+  bool use_ganesh = CanDrawDirectlyToBackbuffer() &&
+                    layer_tree_impl()->settings().force_direct_layer_drawing;
+
+  if (use_ganesh || !append_quads_data->allow_tile_draw_quads) {
     gfx::Rect geometry_rect = rect;
     gfx::Rect opaque_rect = contents_opaque() ? geometry_rect : gfx::Rect();
     gfx::Size texture_size = rect.size();
@@ -116,6 +119,7 @@ void PictureLayerImpl::AppendQuads(QuadSink* quad_sink,
                  false,
                  quad_content_rect,
                  contents_scale,
+                 use_ganesh,
                  pile_);
     if (quad_sink->Append(quad.PassAs<DrawQuad>(), append_quads_data))
       append_quads_data->num_missing_tiles++;
@@ -249,6 +253,7 @@ void PictureLayerImpl::AppendQuads(QuadSink* quad_sink,
                      drawing_info.contents_swizzled(),
                      iter->content_rect(),
                      iter->contents_scale(),
+                     use_ganesh,
                      pile_);
         quad_sink->Append(quad.PassAs<DrawQuad>(), append_quads_data);
         break;
@@ -379,6 +384,19 @@ void PictureLayerImpl::CalculateContentsScale(
   ideal_device_scale_ = ideal_device_scale;
   ideal_source_scale_ = std::max(ideal_source_scale, min_source_scale);
 
+  if (CanDrawDirectlyToBackbuffer() &&
+      layer_tree_impl()->settings().force_direct_layer_drawing) {
+    if (tilings_)
+      tilings_->RemoveAllTilings();
+
+    *contents_scale_x = ideal_contents_scale_;
+    *contents_scale_y = ideal_contents_scale_;
+    *content_bounds = gfx::ToCeiledSize(gfx::ScaleSize(bounds(),
+                                                       ideal_contents_scale_,
+                                                       ideal_contents_scale_));
+    return;
+  }
+
   ManageTilings(animating_transform_to_screen);
 
   // The content scale and bounds for a PictureLayerImpl is somewhat fictitious.