Update ppapi/ to use scoped_refptr<T>::get() rather than implicit "operator T*"

ppapi/proxy/resource_creation_proxy.cc

Index: ppapi/proxy/resource_creation_proxy.cc
diff --git a/ppapi/proxy/resource_creation_proxy.cc b/ppapi/proxy/resource_creation_proxy.cc
index b15f23d7e3f5176785bda1fd41eb841bccd9f9c2..869ecd4af8feb7f4346b82c38d42fe78986d5dfa 100644
--- a/ppapi/proxy/resource_creation_proxy.cc
+++ b/ppapi/proxy/resource_creation_proxy.cc
@@ -228,9 +228,9 @@ PP_Resource ResourceCreationProxy::CreateFileChooser(
     PP_FileChooserMode_Dev mode,
     const PP_Var& accept_types) {
   scoped_refptr<StringVar> string_var = StringVar::FromPPVar(accept_types);
-  std::string str = string_var ? string_var->value() : std::string();
-  return (new FileChooserResource(GetConnection(), instance, mode,
-                                  str.c_str()))->GetReference();
+  std::string str = string_var.get() ? string_var->value() : std::string();
+  return (new FileChooserResource(GetConnection(), instance, mode, str.c_str()))
+      ->GetReference();
 }
 
 PP_Resource ResourceCreationProxy::CreateGraphics2D(PP_Instance instance,