Initial support for native accessibility in ARC

components/exo/surface.cc

Index: components/exo/surface.cc
diff --git a/components/exo/surface.cc b/components/exo/surface.cc
index 01115e7f2cccf801d612a643f4203fb82be38fc0..c232e9e19afde210cf41e274d235037db14f57fd 100644
--- a/components/exo/surface.cc
+++ b/components/exo/surface.cc
@@ -20,6 +20,7 @@
 #include "cc/surfaces/sequence_surface_reference_factory.h"
 #include "cc/surfaces/surface.h"
 #include "cc/surfaces/surface_id_allocator.h"
+#include "components/exo/ax_tree_source_surface.h"
 #include "components/exo/buffer.h"
 #include "components/exo/surface_delegate.h"
 #include "components/exo/surface_observer.h"
@@ -177,7 +178,8 @@ Surface::Surface()
     : window_(new aura::Window(new CustomWindowDelegate(this))),
       frame_sink_id_(aura::Env::GetInstance()
                          ->context_factory_private()
-                         ->AllocateFrameSinkId()) {
+                         ->AllocateFrameSinkId()),
+      ax_tree_source_(nullptr) {
   compositor_frame_sink_holder_ = new CompositorFrameSinkHolder(
       this, frame_sink_id_,
       aura::Env::GetInstance()->context_factory_private()->GetSurfaceManager());