Inline FundamentalValue into base::Value

skia/ext/benchmarking_canvas.cc

Index: skia/ext/benchmarking_canvas.cc
diff --git a/skia/ext/benchmarking_canvas.cc b/skia/ext/benchmarking_canvas.cc
index 32e4df0c1489da408746a8f453248679590a6e6c..d66614a7343d5d458d747b07a568c93d15598852 100644
--- a/skia/ext/benchmarking_canvas.cc
+++ b/skia/ext/benchmarking_canvas.cc
@@ -49,14 +49,14 @@ private:
 std::unique_ptr<base::Value> AsValue(bool b) {
   std::unique_ptr<base::FundamentalValue> val(new base::FundamentalValue(b));
 
-  return std::move(val);
+  return val;
 }
 
 std::unique_ptr<base::Value> AsValue(SkScalar scalar) {
   std::unique_ptr<base::FundamentalValue> val(
       new base::FundamentalValue(scalar));
 
-  return std::move(val);

[jdoerrie, 2017/01/21 15:06:51]

After the typdef this results in a compile error: moving a local object in a
return statement prevents copy elision [-Werror,-Wpessimizing-move]

Therefore this change is necessary.

[brettw, 2017/01/23 05:52:50]

Interesting, I wonder why it didn't complain before, it should definitely be
changed.

[jdoerrie, 2017/01/24 08:59:35]

If I understand this correctly, only after the typedef the type of |val| is
equal to the function return type, resulting in a possibility for return value
optimization (RVO). The presence of |std::move| would prevent RVO, which is why
clang issues a warning.

For the other derived classes (such as |DictionaryValue|) no typedef to |Value|
exists, resulting in the type of |val| to be different than the function return
type. Hence |std::move| does not block RVO, because it could not happen in the
first place.

Reference:
- http://stackoverflow.com/a/12953145

+  return val;
 }
 
 std::unique_ptr<base::Value> AsValue(const SkSize& size) {