- Electron version: 0.37.6
- Operating system: Windows 10

In VSCode, in order to support screen readers while editing text, we set the contents of a `<textarea>` to the contents of the line and lines surrounding the cursor and we mirror the editor selection in the `<textarea>` via `setSelectionRange`.

Chromium is not the fastest when it comes to setting large amounts of text :) (such as > 10,000 characters) and basically stalls all the time. Apparently, Electron already has some knowledge about when a screen reader is attached to the main process window (in C++ code). Is it possible to expose this as a getter + event when it first happens in the `electron` API.

We could then maintain this costly `<textarea>` sync only when really needed.

atom/browser/api/atom_api_app.h
void OnWindowAllClosed() override;
  void OnQuit() override;
  void OnOpenFile(bool* prevent_default, const std::string& file_path) override;
  void OnOpenURL(const std::string& url) override;
  void OnActivate(bool has_visible_windows) override;
  void OnWillFinishLaunching() override;
  void OnFinishLaunching() override;
  void OnLogin(LoginHandler* login_handler,
               const base::DictionaryValue& request_details) override;
#if defined(OS_MACOSX)
  void OnContinueUserActivity(
      bool* prevent_default,
      const std::string& type,
      const base::DictionaryValue& user_info) override;
#endif
  
  void AllowCertificateError(
      content::WebContents* web_contents,
      int cert_error,
      const net::SSLInfo& ssl_info,
      const GURL& request_url,
      content::ResourceType resource_type,
      bool overridable,
      bool strict_enforcement,
      bool expired_previous_decision,
      const base::Callback<void(bool)>& callback,
      content::CertificateRequestResultType* request) override;
  void SelectClientCertificate(
      content::WebContents* web_contents,
      net::SSLCertRequestInfo* cert_request_info,