code/panels/DashboardGridFieldPanel.php
public function gridsforpage(SS_HTTPRequest $r) {
		$pageid = (int) $r->requestVar('pageid');
		return Convert::array2json($this->panel->getGridFieldsFor(SiteTree::get()->byID($pageid)));
	}
public function gridsforpage(SS_HTTPRequest $r) {
		$pageid = (int) $r->requestVar('pageid');
		return Convert::array2json($this->panel->getGridFieldsFor(SiteTree::get()->byID($pageid)));
	}
Given a requested page, get the GridField names and provide a JSON response

@param SS_HTTPRequest The request object
@return string