Disable flaky PrerenderBrowserTest.PrerenderWindowSize on ChromeOS

TBR=mmenke@chromium.org

Bug: 807821
Change-Id: I0e3d42610cea3d87565550dee22e4806959d2893
Reviewed-on: https://chromium-review.googlesource.com/897302Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533597}

chrome/browser/prerender/prerender_browsertest.cc

@@ -2033,7 +2033,13 @@ IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderHTML5VideoNetwork) {
 }
 
 // Checks that scripts can retrieve the correct window size while prerendering.
-IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, PrerenderWindowSize) {
+// Disabled on ChromeOS. See https://crbug.com/807821.
+#if defined(OS_CHROMEOS)
+#define MAYBE_PrerenderWindowSize DISABLED_PrerenderWindowSize
+#else
+#define MAYBE_PrerenderWindowSize PrerenderWindowSize
+#endif
+IN_PROC_BROWSER_TEST_F(PrerenderBrowserTest, MAYBE_PrerenderWindowSize) {
   PrerenderTestURL("/prerender/prerender_size.html", FINAL_STATUS_USED, 1);
   NavigateToDestURL();
 }