Refactor accessible focus ring code so the layers are animation observers.

chrome/browser/chromeos/ui/accessibility_cursor_ring_layer.cc

Index: chrome/browser/chromeos/ui/accessibility_cursor_ring_layer.cc
diff --git a/chrome/browser/chromeos/ui/accessibility_cursor_ring_layer.cc b/chrome/browser/chromeos/ui/accessibility_cursor_ring_layer.cc
index 6d1d776c4389e73c41668908b4ec6304a0265680..df052f71ac18b364e9cbabf815dd227c659dee6a 100644
--- a/chrome/browser/chromeos/ui/accessibility_cursor_ring_layer.cc
+++ b/chrome/browser/chromeos/ui/accessibility_cursor_ring_layer.cc
@@ -50,10 +50,7 @@ void AccessibilityCursorRingLayer::Set(const gfx::Point& location) {
   aura::Window* root_window = ash::Shell::GetInstance()
                                   ->window_tree_host_manager()
                                   ->GetRootWindowForDisplayId(display.id());
-  CreateOrUpdateLayer(root_window, "AccessibilityCursorRing");
-
-  // Update the layer bounds.
-  layer()->SetBounds(bounds);
+  CreateOrUpdateLayer(root_window, "AccessibilityCursorRing", bounds);
 }
 
 void AccessibilityCursorRingLayer::SetOpacity(float opacity) {