Sheriff: Mark PointerLockEventRouting test as flaky

Mark PointerLockBrowserTest.PointerLockEventRouting as flaky on Linux.

TBR=lfg@chromium.org, gab@chromium.org

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 766450
Change-Id: I1932e553b3ae1644241a4e8c8676b121e5710b19
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2142330Reviewed-by: Darwin Huang <huangdarwin@chromium.org>
Commit-Queue: Darwin Huang <huangdarwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757512}

content/browser/pointer_lock_browsertest.cc

@@ -237,8 +237,8 @@ IN_PROC_BROWSER_TEST_F(PointerLockBrowserTest,
                    EXECUTE_SCRIPT_NO_USER_GESTURE));
 }
 
-// Flaky on Windows.  https://crbug.com/992529
-#if defined(OS_WIN)
+// TODO(https://crbug.com/992529): Fix test flakiness on Windows and Linux.
+#if defined(OS_WIN) || defined(OS_LINUX)
 #define MAYBE_PointerLockEventRouting DISABLED_PointerLockEventRouting
 #else
 #define MAYBE_PointerLockEventRouting PointerLockEventRouting