Disables NavigationControllerBrowserTest.EnsureFrameNavigationEntriesClearedOnMismatch

It's flaky on ChromeOS as well.

BUG=897058
TEST=test only change
TBR=lukasza@chromium.org

Change-Id: I11cc721b303a738d1c1b799170887b9b5aa67db6
Reviewed-on: https://chromium-review.googlesource.com/c/1291412Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601201}

content/browser/frame_host/navigation_controller_impl_browsertest.cc

@@ -6573,8 +6573,9 @@ IN_PROC_BROWSER_TEST_F(NavigationControllerBrowserTest,
 // Tests that inserting a named subframe into the FrameTree clears any
 // previously existing FrameNavigationEntry objects for the same name.
 // See https://crbug.com/628677.
-// Crashes inconsistently on windows only: https://crbug.com/783806.
-#if defined(OS_WIN)
+// Crashes/fails inconsistently on windows and ChromeOS:
+// https://crbug.com/783806.
+#if defined(OS_WIN) || defined(OS_CHROMEOS)
 #define MAYBE_EnsureFrameNavigationEntriesClearedOnMismatch \
   DISABLED_EnsureFrameNavigationEntriesClearedOnMismatch
 #else