Disable one flaky SiteIsolation test on ChromeOS

This CL disables
SitePerProcessBrowserTest.ScrollBubblingFromOOPIFWithBodyOverflowHidden
which is flaky on linux-chromeos-rel.

TBR=xidachen@chromium.org, nasko@chromium.org
NOTRY=true

Bug: 836200
Change-Id: If6bd9bad4d852eebfe4fe277f420854b228ed5a4
Reviewed-on: https://chromium-review.googlesource.com/1025694Reviewed-by: Camille Lamy <clamy@chromium.org>
Commit-Queue: Camille Lamy <clamy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553064}

content/browser/site_per_process_browsertest.cc

@@ -1635,6 +1635,14 @@ IN_PROC_BROWSER_TEST_F(SitePerProcessBrowserTest,
   }
 }
 
+#if defined(OS_CHROMEOS)
+// Flaky: https://crbug.com/836200.
+#define MAYBE_ScrollBubblingFromOOPIFWithBodyOverflowHidden \
+  DISABLED_ScrollBubblingFromOOPIFWithBodyOverflowHidden
+#else
+#define MAYBE_ScrollBubblingFromOOPIFWithBodyOverflowHidden \
+  ScrollBubblingFromOOPIFWithBodyOverflowHidden
+#endif
 // Tests that scrolling bubbles from an oopif if its source body has
 // "overflow:hidden" style.
 IN_PROC_BROWSER_TEST_F(SitePerProcessBrowserTest,