Disable AppSearchResultRankerSerializationTest.SaveToDiskSucceed

Test is flaky.

Bug: 884140
Change-Id: I41f4f3eb084edd56867ffecc437817be8f1bcc1b
Reviewed-on: https://chromium-review.googlesource.com/1231037Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Asanka Herath <asanka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592095}

chrome/browser/ui/app_list/search/search_result_ranker/app_search_result_ranker_unittest.cc

@@ -172,7 +172,8 @@ TEST_F(AppSearchResultRankerSerializationTest,
   EXPECT_TRUE(ranker.Rank().empty());
 }
 
-TEST_F(AppSearchResultRankerSerializationTest, SaveToDiskSucceed) {
+// Test is flaky. See https://crbug.com/884140
+TEST_F(AppSearchResultRankerSerializationTest, DISABLED_SaveToDiskSucceed) {
   // Construct ranker.
   AppSearchResultRanker ranker(temp_dir_.GetPath(), kNotAnEphemeralUser);
   // Wait for the loading to finish.