feat(mobileWizard): keep past scroll position

In I02365ecef859fb6f199d14a12a49937d5a30b8e7
(#9230) we made the scroll position of a menu
always return to the top. This was to avoid a bug where a submenu would
keep its scroll, starting partway down and obscuring the top items.

In the review, it was mentioned that it would be even better to keep the
scroll position of the menu when returning to it. For simplicity I've
opted to only keep the position of menus up of you (so exiting a submenu
then reopening it will keep the position of the top menu, but not the
submenu), I make no comment on which way would be better as a user

Signed-off-by: Skyler Grey <[email protected]>
Change-Id: If82ff0b586a65349452fe8ebfb7fa046e4f874fb

browser/src/control/Control.MobileWizardWindow.js

@@ -55,6 +55,8 @@ L.Control.MobileWizardWindow = L.Control.extend({
 		var parentNode = document.getElementById('mobile-wizard-content');
 		this.content = L.DomUtil.create('div', 'mobile-wizard mobile-wizard-content', parentNode);
 		this.content.id = this.id;
+
+		this.scrollPositions = [];
 	},
 
 	onAdd: function (map) {
@@ -253,6 +255,8 @@ L.Control.MobileWizardWindow = L.Control.extend({
 		else
 			$(contentToShow).children('.ui-content').first().show();
 
+		const currentScroll = this.mobileWizard.scrollTop();
+		this.scrollPositions.push(currentScroll);
 		this.mobileWizard.scrollTop(0);
 
 		this._currentDepth++;
@@ -325,7 +329,8 @@ L.Control.MobileWizardWindow = L.Control.extend({
 			$('#mobile-wizard.funcwizard div#mobile-wizard-content').addClass('hideHelpBG');
 			headers.show('slide', { direction: 'left' }, 'fast');
 
-			this.mobileWizard.scrollTop(0);
+			const prevScroll = this.scrollPositions.pop();
+			this.mobileWizard.scrollTop(prevScroll);
 
 			if (this._currentDepth == 0 || (this._isTabMode && this._currentDepth == 1)) {
 				this._inMainMenu = true;