Reduce strictness of length animation DCHECK

third_party/WebKit/LayoutTests/animations/length-zero-percent-crash.html

Index: third_party/WebKit/LayoutTests/animations/length-zero-percent-crash.html
diff --git a/third_party/WebKit/LayoutTests/animations/length-zero-percent-crash.html b/third_party/WebKit/LayoutTests/animations/length-zero-percent-crash.html
new file mode 100644
index 0000000000000000000000000000000000000000..9ef565156f1fa825c312d1d00635c2dda0338064
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/animations/length-zero-percent-crash.html
@@ -0,0 +1,9 @@
+<script src="../resources/testharness.js"></script>
+<script src="../resources/testharnessreport.js"></script>
+<div id="target"></div>
+<script>
+test(() => {
+  target.animate({margin: ['1px', '0%']}, {iterationStart: 0.5, fill: 'forwards'});
+  assert_equals(getComputedStyle(target).margin, '0.5px');
+}, 'Don\'t crash when animating length properties to 0%');

[suzyh_UTC10 (ex-contributor), 2017/02/14 04:38:51]

Nit: I prefer "Don't ..." to 'Don\'t ...', unless there's a style guide rule
I've forgotten.

[alancutter (OOO until 2018), 2017/02/14 04:46:12]

Done.

+</script>