PPAPI: Make blocking completion callbacks work.

ppapi/thunk/ppb_url_loader_thunk.cc

Index: ppapi/thunk/ppb_url_loader_thunk.cc
diff --git a/ppapi/thunk/ppb_url_loader_thunk.cc b/ppapi/thunk/ppb_url_loader_thunk.cc
index 71dbdad2a69bbbfdb93ed774d56ad467878aa90a..7b80aa04f264b710ef992abe477a9540067c527a 100644
--- a/ppapi/thunk/ppb_url_loader_thunk.cc
+++ b/ppapi/thunk/ppb_url_loader_thunk.cc
@@ -34,7 +34,7 @@ int32_t Open(PP_Resource loader,
   EnterURLLoader enter(loader, callback, true);
   if (enter.failed())
     return enter.retval();
-  return enter.SetResult(enter.object()->Open(request_id, callback));
+  return enter.SetResult(enter.object()->Open(request_id, enter.callback()));
 }
 
 int32_t FollowRedirect(PP_Resource loader,
@@ -42,7 +42,7 @@ int32_t FollowRedirect(PP_Resource loader,
   EnterURLLoader enter(loader, callback, true);
   if (enter.failed())
     return enter.retval();
-  return enter.SetResult(enter.object()->FollowRedirect(callback));
+  return enter.SetResult(enter.object()->FollowRedirect(enter.callback()));
 }
 
 PP_Bool GetUploadProgress(PP_Resource loader,
@@ -86,7 +86,7 @@ int32_t ReadResponseBody(PP_Resource loader,
   if (enter.failed())
     return enter.retval();
   return enter.SetResult(enter.object()->ReadResponseBody(buffer, bytes_to_read,
-                                                         callback));
+                                                          enter.callback()));
 }
 
 int32_t FinishStreamingToFile(PP_Resource loader,
@@ -94,7 +94,8 @@ int32_t FinishStreamingToFile(PP_Resource loader,
   EnterURLLoader enter(loader, callback, true);
   if (enter.failed())
     return enter.retval();
-  return enter.SetResult(enter.object()->FinishStreamingToFile(callback));
+  return enter.SetResult(
+      enter.object()->FinishStreamingToFile(enter.callback()));
 }
 
 void Close(PP_Resource loader) {