Aura: Keep the external texture until we've updated compositor references to it.

ui/compositor/layer.cc

Index: ui/compositor/layer.cc
diff --git a/ui/compositor/layer.cc b/ui/compositor/layer.cc
index 9bb17daf8e48bf937adbb2d3b63823184a183a21..c96ac53612f229a1994e0cadef309be998b24e21 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -487,6 +487,10 @@ void Layer::SwitchCCLayerForTest() {
 }
 
 void Layer::SetExternalTexture(Texture* texture) {
+  // Hold a ref to the old |Texture| until we have updated all
+  // compositor references to the texture id that it holds.
+  scoped_refptr<ui::Texture> old_texture = texture_;
+
   DCHECK_EQ(type_, LAYER_TEXTURED);
   DCHECK(!solid_color_layer_);
   bool has_texture = !!texture;