[gparted] Pass message parameters by reference to 2 Partition methods (#788813)

[Curtis Gedak <gedakc src gnome org>]

commit 454ac64d1905ade9576cd09bb9ef5555d795c619
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Sat Mar 23 10:19:09 2019 +0000

    Pass message parameters by reference to 2 Partition methods (#788813)
    
    Note that this almost certainly has no performance benefit what so ever
    because the methods are implicitly defined as inline [1][2] and the
    compiler will have simply inlined the method bodies thus avoiding having
    to construct copies of the passed parameters.
    
    Do this anyway as constant objects are typically passed by reference
    [3].  Also C++'s std::vector::push_back() [4] takes a const reference
    parameter so update the kind of equivalent push_back_message() to take
    a const reference parameter too.
    
    [1] C++ reference / inline specifier
        https://en.cppreference.com/w/cpp/language/inline
    
            A function defined entirely inside a class/struct/union
            definition, whether it's a member function or a non-member
            friend function, is implicitly an inline function.
    
    [2] When should I write the keyword 'inline' for a function/method?
        
https://stackoverflow.com/questions/1759300/when-should-i-write-the-keyword-inline-for-a-function-method/1759575#1759575
    
    [3] How to pass objects to functions in C++?
        https://stackoverflow.com/questions/2139224/how-to-pass-objects-to-functions-in-c/2139254#2139254
    
    [4] C++ reference / std::vector::push
        https://en.cppreference.com/w/cpp/container/vector/push_back
    
            void push_back(const T& value);
    
    Bug 788813 - gparted-0.30.0/include/Partition.h:137]: performance
                 problem

 include/Partition.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/include/Partition.h b/include/Partition.h
index da2dac2b..87b103ca 100644
--- a/include/Partition.h
+++ b/include/Partition.h
@@ -133,8 +133,8 @@ public:
        virtual bool have_messages() const                             { return ! messages.empty(); };
        virtual std::vector<Glib::ustring> get_messages() const        { return messages; };
        virtual void clear_messages()                                  { messages.clear(); };
-       void push_back_message( Glib::ustring msg )                    { messages.push_back( msg ); };
-       void append_messages( const std::vector<Glib::ustring> msgs )
+       void push_back_message(const Glib::ustring& msg)               { messages.push_back(msg); };
+       void append_messages(const std::vector<Glib::ustring>& msgs)
                                        { messages.insert( messages.end(), msgs.begin(), msgs.end() ); }
 
        // Interface to return reference to the Partition object directly containing the