[BrowserSwitcher] Disable flaky test

TBR: pastarmovj@chromium.org
Bug: 1079242
Change-Id: I78eaff424ef6d580c03be7a06fac3b8343746ab5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2188237Reviewed-by: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Commit-Queue: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Cr-Commit-Position: refs/heads/master@{#766515}

chrome/browser/browser_switcher/browser_switcher_service_browsertest.cc

@@ -560,7 +560,8 @@ IN_PROC_BROWSER_TEST_F(BrowserSwitcherServiceTest, WritesPrefsToCacheFile) {
   EXPECT_FALSE(base::PathExists(sitelist_cache_file_path()));
 }
 
-IN_PROC_BROWSER_TEST_F(BrowserSwitcherServiceTest, WritesSitelistsToCacheFile) {
+IN_PROC_BROWSER_TEST_F(BrowserSwitcherServiceTest,
+                       DISABLED_WritesSitelistsToCacheFile) {
   base::ScopedAllowBlockingForTesting allow_blocking;
 
   base::ScopedTempDir dir;