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/atom_web_ui_controller_factory.cc

@@ -52,7 +52,7 @@ AtomWebUIControllerFactory::CreateWebUIControllerForURL(content::WebUI* web_ui,
   if (url.host() == kPdfViewerUIHost) {
     base::StringPairs toplevel_params;
     base::SplitStringIntoKeyValuePairs(url.query(), '=', '&', &toplevel_params);
-    std::string stream_id, src;
+    std::string src;
 
     const net::UnescapeRule::Type unescape_rules =
       net::UnescapeRule::SPACES | net::UnescapeRule::PATH_SEPARATORS |