You need to redefine what it does /openerp/addons/report/static/src/js/qwebactionmanager.js

Like this in your own module js

odoo.define('module.report', function (require) {

var ActionManager = require('web.ActionManager');
var core = require('web.core');
var crash_manager = require('web.crash_manager');
var framework = require('web.framework');
var session = require('web.session');

var _t = core._t;
var wkhtmltopdf_state;

var trigger_download = function(session, response, c, action, options) {
 session.get_file({
 url: '/report/download',
 data: {data: JSON.stringify(response)},
 complete: framework.unblockUI,
 error: c.rpc_error.bind(c),
 success: function(){
 if (action && options && !action.dialog) {
 options.on_close();
 }
 },
 });
};

ActionManager.include({
 ir_actions_report_xml: function(action, options) {
 var self = this;
 framework.blockUI();
 action = _.clone(action);
 _t = core._t;

 // QWeb reports
 if ('report_type' in action && (action.report_type == 'qweb-html' || action.report_type == 'qweb-pdf' || action.report_type == 'controller')) {
 var report_url = '';
 switch (action.report_type) {
 case 'qweb-html':
 report_url = '/report/html/' + action.report_name;
 break;
 case 'qweb-pdf':
 report_url = '/report/pdf/' + action.report_name;
 break;
 case 'controller':
 report_url = action.report_file;
 break;
 default:
 report_url = '/report/html/' + action.report_name;
 break;
 }

 // generic report: no query string
 // particular: query string of action.data.form and context
 if (!('data' in action) || !(action.data)) {
 if ('active_ids' in action.context) {
 report_url += "/" + action.context.active_ids.join(',');
 }
 } else {
 report_url += "?options=" + encodeURIComponent(JSON.stringify(action.data));
 report_url += "&context=" + encodeURIComponent(JSON.stringify(action.context));
 }

 var response = new Array();
 response[0] = report_url;
 response[1] = action.report_type;
 var c = crash_manager;

 if (action.report_type == 'qweb-html') {
 window.open(report_url, '_blank', 'scrollbars=1,height=900,width=1280');
 framework.unblockUI();
 } else if (action.report_type === 'qweb-pdf') {
 // Trigger the download of the pdf/controller report
 (wkhtmltopdf_state = wkhtmltopdf_state || session.rpc('/report/check_wkhtmltopdf')).then(function (presence) {
 // Fallback on html if wkhtmltopdf is not installed or if OpenERP is started with one worker
 if (presence === 'install') {
 self.do_notify(_t('Report'), _t('Unable to find Wkhtmltopdf on this \
system. The report will be shown in html.<br><br><a href="http://wkhtmltopdf.org/" target="_blank">\
wkhtmltopdf.org</a>'), true);
 report_url = report_url.substring(12);
 window.open('/report/html/' + report_url, '_blank', 'height=768,width=1024');
 framework.unblockUI();
 return;
 } else if (presence === 'workers') {
 self.do_notify(_t('Report'), _t('You need to start OpenERP with at least two \
workers to print a pdf version of the reports.'), true);
 report_url = report_url.substring(12);
 window.open('/report/html/' + report_url, '_blank', 'height=768,width=1024');
 framework.unblockUI();
 return;
 } else if (presence === 'upgrade') {
 self.do_notify(_t('Report'), _t('You should upgrade your version of\
Wkhtmltopdf to at least 0.12.0 in order to get a correct display of headers and footers as well as\
support for table-breaking between pages.<br><br><a href="http://wkhtmltopdf.org/" \
target="_blank">wkhtmltopdf.org</a>'), true);
 }
 return trigger_download(self.session, response, c, action, options);
 });
 } else if (action.report_type === 'controller') {
 return trigger_download(self.session, response, c, action, options);
 } 
 } else {
 return self._super(action, options);
 }
 }
});

});