Add GetLiveVars to PPB_Testing_Dev. Fix leaks it uncovered.

ppapi/proxy/serialized_var.cc

Index: ppapi/proxy/serialized_var.cc
diff --git a/ppapi/proxy/serialized_var.cc b/ppapi/proxy/serialized_var.cc
index b892daf0b935322054f48556ccb0e8898846c1c4..f9d59e5e6c9120cbd779594f1474abe830c7ece6 100644
--- a/ppapi/proxy/serialized_var.cc
+++ b/ppapi/proxy/serialized_var.cc
@@ -411,7 +411,7 @@ PP_Var* SerializedVarVectorReceiveInput::Get(Dispatcher* dispatcher,
                                              uint32_t* array_size) {
   deserialized_.resize(serialized_.size());
   for (size_t i = 0; i < serialized_.size(); i++) {
-    // The vector must be able to clean themselves up after this call is
+    // The vectors must be able to clean themselves up after this call is
     // torn down.
     serialized_[i].inner_->set_serialization_rules(
         dispatcher->serialization_rules());