Fix cppcheck warnings (#11883)

* remove unused variable

* limit scope of variable 'ret'

* pass shared_ptr<SkBitmap> by reference

* silence warning: value reassign before read

* fix oops

* don't refer to 'response' after std::move()ing it

* make the linter happy

atom/browser/osr/osr_render_widget_host_view.cc

@@ -194,7 +194,7 @@ class AtomCopyFrameGenerator {
 
   void OnCopyFrameCaptureSuccess(
       const gfx::Rect& damage_rect,
-      std::shared_ptr<SkBitmap> bitmap) {
+      const std::shared_ptr<SkBitmap>& bitmap) {
     base::AutoLock lock(onPaintLock_);
     view_->OnPaint(damage_rect, *bitmap);
   }