Themes: Add a clearing <br/> to the end of .theme-browser.

This is needed to cause the browser to render .theme-browser's height as it's true height, previously the reported height was 1*.theme which caused the Theme scroller to kick in immediately (as the threshold was less than 0).
See #25981 See #25948


git-svn-id: https://develop.svn.wordpress.org/trunk@26468 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/js/theme.js

@@ -52,6 +52,7 @@ themes.view.Appearance = wp.Backbone.View.extend({
 		// Render and append
 		this.view.render();
 		this.$el.append( this.view.el );
+		this.$el.append( '<br class="clear"/>' );
 	},
 
 	// Search input and view