Disable PrerenderTest.LinkManagerAddTwiceCancelTwice on Mac and Linux

This test is flaky on Mac and Linux:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=unit_tests%20(with%20patch)&tests=PrerenderTest.LinkManagerAddTwiceCancelTwice

TBR=ryansturm@chromium.org

Bug: 1087735
Change-Id: I2b1235e43423eed9585db89552c4ced769076311
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2232815Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#775728}

chrome/browser/prerender/prerender_unittest.cc

@@ -1537,7 +1537,8 @@ TEST_F(PrerenderTest, LinkManagerAbandonThenCancel) {
 }
 
 // Flaky on Android, crbug.com/1087876.
-#if defined(OS_ANDROID)
+// Flaky on Mac and Linux, crbug.com/1087735.
+#if defined(OS_ANDROID) || defined(OS_MACOSX) || defined(OS_LINUX)
 #define MAYBE_LinkManagerAddTwiceCancelTwice \
   DISABLED_LinkManagerAddTwiceCancelTwice
 #else