Mozilla added Plugin Hang User interface to Firefox on Windows which helps users in killing  not responding plugins like Flash straight from the dialog interface. With OOPS in place for Firefox browser Mozilla able to prevent plugins from crashing the browser. When a page with plugin content stops responding Firefox waits for 45 seconds and then kills the plugin. User need to reload the page to see plugin content again. Now during this 45 seconds “Firefox appears to be locked and not doesn’t respond”.

Firefox 19 to get Plugin Hang User interface

During this time period of 45 seconds Firefox shows Plugin Hang UI with options for the user to let the plugin to become working again or stop the plugin.

“This feature will improve the user experience of a plugin not responding by showing UI which allows the user to see that it is the plugin (not Firefox) which is broken, and allowing the user to kill the plugin right away if they don’t want to wait. “

When this UI is invoked you can see child process plugin-hang-ui.exe running under processes list on Task Manager. Currently this feature is targeted for Firefox 19 on Windows.

Firefox plugin hang UI dialog box

Users can able to disable this Plugin Hang UI by setting dom.ipc.plugins.hangUITimeoutSecs preference value to zero in about:config.

Try build available for you to try out the feature.

Source: Aaron klotz at Mozilla