PPAPI: Make blocking completion callbacks work.

webkit/plugins/ppapi/ppb_layer_compositor_impl.cc

Index: webkit/plugins/ppapi/ppb_layer_compositor_impl.cc
diff --git a/webkit/plugins/ppapi/ppb_layer_compositor_impl.cc b/webkit/plugins/ppapi/ppb_layer_compositor_impl.cc
index 542feb1ef1a6a035793d79902304b970177e3223..32b859a1f139ccd363859bbf59081ababae31371 100644
--- a/webkit/plugins/ppapi/ppb_layer_compositor_impl.cc
+++ b/webkit/plugins/ppapi/ppb_layer_compositor_impl.cc
@@ -5,8 +5,10 @@
 #include "webkit/plugins/ppapi/ppb_layer_compositor_impl.h"
 
 #include "ppapi/c/pp_errors.h"
+#include "ppapi/shared_impl/tracked_callback.h"
 #include "webkit/plugins/ppapi/common.h"
 
+using ppapi::TrackedCallback;
 using ppapi::thunk::PPB_LayerCompositor_API;
 
 namespace webkit {
@@ -45,7 +47,8 @@ void PPB_LayerCompositor_Impl::SetDisplay(PP_Resource layer,
 void PPB_LayerCompositor_Impl::MarkAsDirty(PP_Resource layer) {
 }
 
-int32_t PPB_LayerCompositor_Impl::SwapBuffers(PP_CompletionCallback callback) {
+int32_t PPB_LayerCompositor_Impl::SwapBuffers(
+    scoped_refptr<TrackedCallback> callback) {
   return PP_ERROR_FAILED;
 }