Increase the count variable by one, each time the header is double-clicked:
Definition and Usage
ng-dblclick directive tells AngularJS what to do when an HTML
element is double-clicked.
ng-dblclick directive from AngularJS will not override the element's original ondblclick event,
both are executed.
Supported by all HTML elements.
|expression||An expression to execute when an element is cdouble-licked.|