2.12 notes - explain how to disable hw accelerated animations (refs #542)

notes/2.12.md

@@ -95,6 +95,19 @@ Corresponding issues/pull requests:
 
  * https://github.com/openlayers/openlayers/pull/127
 
+Note: Issue #511 has reported that tile animation causes flickering/blinking in
+the iOS native browser. Forcing the browser to use hardware-accelerated
+animations fixed the issue, but #542 has reported that it also considerably
+slows down freehand drawing on iOS. If you're experiencing this and want to
+disable hardware-accelerated animations you can use the following rule in your
+CSS:
+
+    @media (-webkit-transform-3d) {
+        img.olTileImage {
+            -webkit-transform: none;
+        }
+    }
+
 ## Tile Queue
 
 The tiling code has been overhauled so tile loading in grid layers is now done in a queue.