MDL-37566 AJAX Fix issues with minimum height and centring

Conflicts:
	lib/yui/chooserdialogue/chooserdialogue.js

lib/yui/chooserdialogue/chooserdialogue.js

@@ -239,8 +239,21 @@ YUI.add('moodle-core-chooserdialogue', function(Y) {
             newheight = newheight - (15 + 15 + 40 + 40);
             dialogue.setStyle('maxHeight', newheight + 'px');
 
+            dialogueheight = bb.getStyle('height');
+            if (dialogueheight.match(/.*px$/)) {
+                dialogueheight = dialogueheight.replace(/px$/, '');
+            } else {
+                dialogueheight = totalheight;
+            }
+
+            if (dialogueheight < this.get('baseheight')) {
+                dialogueheight = this.get('baseheight');
+                dialogue.setStyle('height', dialogueheight + 'px');
+            }
+
+
             // Re-calculate the location now that we've changed the size
-            var dialoguetop = Math.max(12, ((winheight - totalheight) / 2)) + offsettop;
+            dialoguetop = Math.max(12, ((winheight - dialogueheight) / 2)) + offsettop;
 
             // We need to set the height for the yui3-widget - can't work
             // out what we're setting at present -- shoud be the boudingBox
@@ -312,6 +325,9 @@ YUI.add('moodle-core-chooserdialogue', function(Y) {
             minheight : {
                 value : 300
             },
+            baseheight: {
+                value : 400
+            },
             maxheight : {
                 value : 660
             },