Disable TabSpinnerTest.LoadTabsOneByOne on linux-chromeos-debug.

TabSpinnerTest.LoadTabsOneByOne is timeout on linux-chromeos-debug.
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=interactive_ui_tests&tests=TabSpinnerTest.LoadTabsOneByOne

Bug: 974349
Change-Id: Iaa850ebf45f7d4c301d3d0cd581cc771c917cc5f
Tbr: estade@chromium.org, anniesu@google.com
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1761877Reviewed-by: Takashi Sakamoto <tasak@google.com>
Commit-Queue: Takashi Sakamoto <tasak@google.com>
Cr-Commit-Position: refs/heads/master@{#688448}

chrome/browser/ui/views/tabs/tab_spinner_interactive_uitest.cc

@@ -59,7 +59,13 @@ class TabSpinnerTest : public UIPerformanceTest {
   DISALLOW_COPY_AND_ASSIGN(TabSpinnerTest);
 };
 
-IN_PROC_BROWSER_TEST_F(TabSpinnerTest, LoadTabsOneByOne) {
+// TODO(974349) This test is timeout on linux-chromeos-dbg.
+#if defined(OS_CHROMEOS) && !defined(NDEBUG)
+#define MAYBE_LoadTabsOneByOne DISABLED_LoadTabsOneByOne
+#else
+#define MAYBE_LoadTabsOneByOne LoadTabsOneByOne
+#endif
+IN_PROC_BROWSER_TEST_F(TabSpinnerTest, MAYBE_LoadTabsOneByOne) {
   IgnorePriorHistogramSamples();
 
   // Navigate to a custom page that takes 10 seconds to load. Wait for the