chromeos: disables SitePerProcessHitTestBrowserTest.CrossProcessMouseCapture

It's flakey, and has been flakey for quite a while.

BUG=868409
TEST=test only change
TBR=riajiang@chromium.org

Change-Id: I4d4a57c9eed04563cdad114075c197244ea7ccdd
Reviewed-on: https://chromium-review.googlesource.com/1153207Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578679}

content/browser/site_per_process_hit_test_browsertest.cc

@@ -2360,8 +2360,14 @@ IN_PROC_BROWSER_TEST_P(SitePerProcessHitTestBrowserTest,
 // TODO(kenrb): This currently only works for scrollbar dragging.
 // Other reasons for a node to capture mouse input need to be addressed. See
 // https://crbug.com/647378.
+#if defined(OS_CHROMEOS)
+// TODO: Flaky on Chrome OS. crbug.com/868409
+#define MAYBE_CrossProcessMouseCapture DISABLED_CrossProcessMouseCapture
+#else
+#define MAYBE_CrossProcessMouseCapture CrossProcessMouseCapture
+#endif
 IN_PROC_BROWSER_TEST_P(SitePerProcessHitTestBrowserTest,
-                       CrossProcessMouseCapture) {
+                       MAYBE_CrossProcessMouseCapture) {
   GURL main_url(embedded_test_server()->GetURL(
       "/frame_tree/page_with_large_scrollable_frame.html"));
   EXPECT_TRUE(NavigateToURL(shell(), main_url));