Remove "static:" element type from animation-test-helpers.js

LayoutTests/animations/cross-fade-background-image.html

Index: LayoutTests/animations/cross-fade-background-image.html
diff --git a/LayoutTests/animations/cross-fade-background-image.html b/LayoutTests/animations/cross-fade-background-image.html
index c37264b8bba51defdd9bff93d4b15f63a0ce7741..f5d5deb61e1adb634d71e5e6b990d12f47304a57 100644
--- a/LayoutTests/animations/cross-fade-background-image.html
+++ b/LayoutTests/animations/cross-fade-background-image.html
@@ -42,8 +42,8 @@
     const expectedValues = [
       // [time, element-id, property, expected-value, tolerance]
       [2.5, "box", "backgroundImage", 0.5, 0.05],
-      [2.5, ["box", "static:boxStatic"], "backgroundImage", 0.5, 0.05],
-      [2.5, ["boxShorthand", "static:boxStatic"], "backgroundImage", 0.5, 0.05],
+      [2.5, ["box", "boxStatic"], "backgroundImage", 0.5, 0.05],
+      [2.5, ["boxShorthand", "boxStatic"], "backgroundImage", 0.5, 0.05],
     ];
 
     var doPixelTest = true;