Update layout test expectations.

Bug: 906952,906879
Change-Id: I0c7bec172a28b37c8b8c3c8e33c7e2f1630d8404
Tbr: kolos@chromium.org
Tbr: pavely@chromium.org
Tbr: hongjunchoi@chromium.org
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/1343475Reviewed-by: Yuta Kitamura <yutak@chromium.org>
Commit-Queue: Yuta Kitamura <yutak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609616}

third_party/WebKit/LayoutTests/TestExpectations

@@ -5401,3 +5401,9 @@ crbug.com/905827 [ Mac10.13 ] fast/dom/StyleSheet/stylesheet-move-between-docume
 #Sheriff 2018-11-19
 crbug.com/906591 printing/single-line-must-not-be-split-into-two-pages.html [ Failure ]
 crbug.com/906591 virtual/threaded/printing/single-line-must-not-be-split-into-two-pages.html [ Failure ]
+
+# Flaky crash due to "bad mojo message".
+crbug.com/906952 editing/pasteboard/file-drag-to-editable.html [ Pass Crash ]
+crbug.com/906952 fast/events/before-unload-return-value-from-listener.html [ Pass Crash ]
+
+crbug.com/906879 http/tests/inspector-protocol/network/navigation-blocking-xorigin-iframe.js [ Pass Failure ]