To repro:

1. Launch an Electron app (hello world/default fiddle will do)
2. Open DevTools
3. Find a minified JS file, e.g. renderer_init.js
4. Click the "Pretty Print" button in DevTools

Expected behavior:
The JS in the DevTools view is replaced with a pretty-printed version of the code

Actual behavior:
The JS in the DevTools view is unchanged


Bisected to https://github.com/electron/electron/compare/v11.0.0-nightly.20200721...v11.0.0-nightly.20200723
shell/browser/ui/devtools_ui.cc
public:
  BundledDataSource() = default;
  ~BundledDataSource() override = default;
  
  std::string GetSource() override { return chrome::kChromeUIDevToolsHost; }
  void StartDataRequest(const GURL& url,
                        const content::WebContents::Getter& wc_getter,
                        GotDataCallback callback) override {
    const std::string path = content::URLDataSource::URLToRequestPath(url);
    
    std::string bundled_path_prefix(chrome::kChromeUIDevToolsBundledPath);
    bundled_path_prefix += "/";
    if (base::StartsWith(path, bundled_path_prefix,
                         base::CompareCase::INSENSITIVE_ASCII)) {
      StartBundledDataRequest(path.substr(bundled_path_prefix.length()),
                              std::move(callback));
      return;
    }
    
    std::move(callback).Run(nullptr);
  }
  std::string GetMimeType(const std::string& path) override {