Disabling PageLoadMetricsBrowserTest.CSSTiming on Linux: flaky

TBR=bmcquade@chromium.org

Bug: 754158
Change-Id: Iaf94b7a4c3c2d0413b3aa838f7ef3f78c98a82c5
Reviewed-on: https://chromium-review.googlesource.com/609064
Reviewed-by: Olga Sharonova <olka@chromium.org>
Commit-Queue: Olga Sharonova <olka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#493356}

chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc

@@ -952,7 +952,13 @@ IN_PROC_BROWSER_TEST_F(PageLoadMetricsBrowserTest,
       "Prerender.none_PrefetchTTFCP.Reference.Cacheable.Visible", 0);
 }
 
-IN_PROC_BROWSER_TEST_F(PageLoadMetricsBrowserTest, CSSTiming) {
+// Flaky on Linux: http://crbug.com/754158.
+#if defined(OS_LINUX)
+#define MAYBE_CSSTiming DISABLED_CSSTiming
+#else
+#define MAYBE_CSSTiming CSSTiming
+#endif
+IN_PROC_BROWSER_TEST_F(PageLoadMetricsBrowserTest, MAYBE_CSSTiming) {
   ASSERT_TRUE(embedded_test_server()->Start());
 
   auto waiter = CreatePageLoadMetricsWaiter();