Assert event timestamp to be monotonic and not from future

components/test_runner/web_test_delegate.h

Index: components/test_runner/web_test_delegate.h
diff --git a/components/test_runner/web_test_delegate.h b/components/test_runner/web_test_delegate.h
index 145a5efa842138e4892f04fb182e4d4735d0073f..dcf16d0afbf065d1ff3fe60148dda16139a3528b 100644
--- a/components/test_runner/web_test_delegate.h
+++ b/components/test_runner/web_test_delegate.h
@@ -276,6 +276,9 @@ class WebTestDelegate {
 
   // Run all pending idle tasks, and then run callback.
   virtual void RunIdleTasks(const base::Closure& callback) = 0;
+
+  virtual void SetMockMonotonicTimeFunction(
+      const base::Callback<double()>& time_function) const = 0;
 };
 
 }  // namespace test_runner