Graceful idle callback cancellation with invalid IDs.

third_party/WebKit/LayoutTests/virtual/threaded/fast/idle-callback/basic.html

Index: third_party/WebKit/LayoutTests/virtual/threaded/fast/idle-callback/basic.html
diff --git a/third_party/WebKit/LayoutTests/virtual/threaded/fast/idle-callback/basic.html b/third_party/WebKit/LayoutTests/virtual/threaded/fast/idle-callback/basic.html
index 0b0e410235c52063664c9c88564554cc404a41bd..b28b109d895d5e7f3aa15649ad61547afca878d5 100644
--- a/third_party/WebKit/LayoutTests/virtual/threaded/fast/idle-callback/basic.html
+++ b/third_party/WebKit/LayoutTests/virtual/threaded/fast/idle-callback/basic.html
@@ -22,6 +22,11 @@ test(function() {
   assert_equals(typeof window.cancelIdleCallback(1), "undefined");
 }, "window.cancelIdleCallback() returns undefined", {assert: "The cancelIdleCallback method MUST return void"});
 
+test(function() {
+  assert_equals(typeof window.cancelIdleCallback(-1), "undefined");
+  assert_equals(typeof window.cancelIdleCallback(0), "undefined");
+}, "window.cancelIdleCallback() returns undefined for unmapped IDs", {assert: "The cancelIdleCallback method MUST return void"});
+
 async_test(function() {
   // Check whether requestIdleCallback schedules a callback which gets executed
   // and the deadline argument is passed correctly.