Attach scrolling handler to canvas_div

Conflicts:
	lib/matplotlib/backends/web_backend/mpl.js

Author: blink1073

lib/matplotlib/backends/web_backend/mpl.js

@@ -46,6 +46,7 @@ mpl.figure = function(figure_id, websocket, ondownload, parent_element) {
     this._root_extra_style(this.root)
     this.root.attr('style', 'display: inline-block');
 
+    this.parent_element = parent_element
     $(parent_element).append(this.root);
 
     this._init_header(this);
@@ -94,6 +95,7 @@ mpl.figure.prototype._init_header = function() {
     this.header = titletext[0];
 }
 
+
 mpl.figure.prototype._canvas_extra_style = function(canvas_div) {
 
 }
@@ -168,6 +170,7 @@ mpl.figure.prototype._init_canvas = function() {
     // upon first draw.
     this._resize_canvas(600, 600);
 
+
     function set_focus () {
         canvas.focus();
         canvas_div.focus();