Filtering MutationObserver polyfill messages from test_controller logging

pkg/unittest/lib/test_controller.js

Index: pkg/unittest/lib/test_controller.js
diff --git a/pkg/unittest/lib/test_controller.js b/pkg/unittest/lib/test_controller.js
index 68b83bfe0a33f260a8ec4bcc9285d8c2b7868975..f78fbde73359ed5487ae2a447cddeb02c72b5374 100644
--- a/pkg/unittest/lib/test_controller.js
+++ b/pkg/unittest/lib/test_controller.js
@@ -89,11 +89,14 @@ function notifyDone() {
 }
 
 function processMessage(msg) {
+  if (typeof msg != 'string') return;
   // TODO(ricow): REMOVE, debug info, see issue 13292
   if (!testRunner) {
-    printMessage('processMessage(): ' + msg);
+    // Filter out ShadowDOM polyfill messages which are random floats.
+    if (msg != parseFloat(msg)) {
+      printMessage('processMessage(): ' + msg);
+    }
   }
-  if (typeof msg != 'string') return;
   if (msg == 'unittest-suite-done') {
     notifyDone();
   } else if (msg == 'unittest-suite-wait-for-done') {