Inline image css to fix selector perf, was about 3%

css/app.css

@@ -22,6 +22,13 @@ body {
     box-sizing: border-box;
 }
 
+/* Mobile Tweaks
+------------------------------------------------------- */
+* {
+    -webkit-tap-highlight-color:rgba(0,0,0,0);
+    -webkit-touch-callout:none;
+}
+
 h2 {
     font-size: 25px;
     line-height: 1.6;
@@ -1035,9 +1042,4 @@ div.typeahead a:first-child {
     left: 30px;
     }
 
-/* Mobile Tweaks
-------------------------------------------------------- */
-* {
-    -webkit-tap-highlight-color:rgba(0,0,0,0);
-    -webkit-touch-callout:none;
-}
+

js/id/renderer/background.js

@@ -6,6 +6,12 @@ iD.Background = function() {
         transformProp = iD.util.prefixCSSProperty('Transform'),
         source = d3.functor('');
 
+    var imgstyle = 'position:absolute;transform-origin:0 0;' +
+        '-ms-transform-origin:0 0;' +
+        '-webkit-transform-origin:0 0;' +
+        '-moz-transform-origin:0 0;' +
+        '-o-transform-origin:0 0;';
+
     function atZoom(t, distance) {
         var power = Math.pow(2, distance);
         var az = [
@@ -82,7 +88,7 @@ iD.Background = function() {
         }
 
         image.enter().append('img')
-            .attr('class', 'tile')
+            .attr('style', imgstyle)
             .attr('src', function(d) { return d[3]; })
             .on('error', error)
             .on('load', load);