Inline StringValue into base::Value

chrome/browser/extensions/api/streams_private/streams_private_api.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/api/streams_private/streams_private_api.h"
 
 #include <limits.h>
 #include <utility>
 
 #include "base/lazy_instance.h"
@@ skipping 21 matching lines @@
     return;
 
   size_t iter = 0;
   std::string header_name;
   std::string header_value;
   while (headers->EnumerateHeaderLines(&iter, &header_name, &header_value)) {
     base::Value* existing_value = NULL;
     if (result->Get(header_name, &existing_value)) {
       base::StringValue* existing_string_value =
           static_cast<base::StringValue*>(existing_value);
-      existing_string_value->GetString()->append(", ").append(header_value);
+      *existing_string_value = base::StringValue(
+          existing_string_value->GetString() + ", " + std::move(header_value));

[brettw, 2017/01/31 22:22:24]

This use of std::move seems not to be helpful to me. I think you should just be
able to do "+ header_value" since it will be passed by const ref into operator+
either way.

[jdoerrie, 2017/02/01 12:36:26]

C++11 introduced overloads for operator+ that take rvalues:
http://en.cppreference.com/w/cpp/string/basic_string/operator%2B

There might be some use for std::move here, but it does feel like a
micro-optimization, so I removed it.

I inlined |existing_string_value|, since the cast to |StringValue| should be a
no-op now and is not needed anymore.

     } else {
       result->SetString(header_name, header_value);
     }
   }
 }
 
 }  // namespace
 
 namespace streams_private = api::streams_private;
 
@@ skipping 132 matching lines @@
 static base::LazyInstance<BrowserContextKeyedAPIFactory<StreamsPrivateAPI> >
     g_factory = LAZY_INSTANCE_INITIALIZER;
 
 // static
 BrowserContextKeyedAPIFactory<StreamsPrivateAPI>*
 StreamsPrivateAPI::GetFactoryInstance() {
   return g_factory.Pointer();
 }
 
 }  // namespace extensions