VertexLoaderManager: Return debug strings by value

This also renames AppendListToString to VertexLoadersToString.

Source/Core/VideoCommon/Statistics.cpp

@@ -68,8 +68,7 @@ std::string Statistics::ToString()
   str += StringFromFormat("Uniform streamed: %i kB\n", stats.thisFrame.bytesUniformStreamed / 1024);
   str += StringFromFormat("Vertex Loaders: %i\n", stats.numVertexLoaders);
 
-  std::string vertex_list;
-  VertexLoaderManager::AppendListToString(&vertex_list);
+  std::string vertex_list = VertexLoaderManager::VertexLoadersToString();
 
   // TODO : at some point text1 just becomes too huge and overflows, we can't even read the added
   // stuff

Source/Core/VideoCommon/VertexLoaderManager.cpp

@@ -98,7 +98,7 @@ struct entry
 };
 }
 
-void AppendListToString(std::string* dest)
+std::string VertexLoadersToString()
 {
   std::lock_guard<std::mutex> lk(s_vertex_loader_map_lock);
   std::vector<entry> entries;
@@ -112,13 +112,18 @@ void AppendListToString(std::string* dest)
     total_size += e.text.size() + 1;
     entries.push_back(std::move(e));
   }
+
   sort(entries.begin(), entries.end());
-  dest->reserve(dest->size() + total_size);
+
+  std::string dest;
+  dest.reserve(total_size);
   for (const entry& entry : entries)
   {
-    *dest += entry.text;
-    *dest += '\n';
+    dest += entry.text;
+    dest += '\n';
   }
+
+  return dest;
 }
 
 void MarkAllDirty()

Source/Core/VideoCommon/VertexLoaderManager.h

@@ -30,7 +30,7 @@ NativeVertexFormatMap* GetNativeVertexFormatMap();
 int RunVertices(int vtx_attr_group, int primitive, int count, DataReader src, bool is_preprocess);
 
 // For debugging
-void AppendListToString(std::string* dest);
+std::string VertexLoadersToString();
 
 NativeVertexFormat* GetCurrentVertexFormat();