Improve unmapper file heuristic, add limited warning support, and ign…

…ore internal errors (#2128)

* Browser sort is not stable

* Fix ordering of final message

* Register the warning capture

* Display only createElement warnings

* Use different method name

* Fix regression

* Ignore errors with only node_module files

* Ignore null files, too

* Revise count

* Revise warning

* Update overlay.js

* Add support for facebook/react#9679

* Use absolute paths

* Trim path if it's absolute

* Make sure it's an absolute path

* Oops

* Tweak for new behavior

* Make it safer

* More resilient warnings

* Prettier output

* Fix flow

config/webpack.config.dev.js

@@ -77,7 +77,7 @@ module.exports = {
     publicPath: publicPath,
     // Point sourcemap entries to original disk location
     devtoolModuleFilenameTemplate: info =>
-      path.relative(paths.appSrc, info.absoluteResourcePath),
+      path.resolve(info.absoluteResourcePath),
   },
   resolve: {
     // This allows you to set a fallback for where Webpack should look for modules.