appDisplay: sync page when changing adjustment

We were setting the value of adjustment on size changes, but we weren't
changing the page value, so adjustment and page value was not in sync.

To fix it, make sure adjustment of the view is in sync with the page
value.

https://bugzilla.gnome.org/show_bug.cgi?id=734680

js/ui/appDisplay.js

@@ -630,6 +630,7 @@ const AllView = new Lang.Class({
 
         if (this._availWidth != availWidth || this._availHeight != availHeight || oldNPages != this._grid.nPages()) {
             this._adjustment.value = 0;
+            this._currentPage = 0;
             Meta.later_add(Meta.LaterType.BEFORE_REDRAW, Lang.bind(this,
                 function() {
                     this._pageIndicators.setNPages(this._grid.nPages());