Disable flaky BasicSelectionIsolatedScrollMainframe

TouchSelectionForCrossProcessFramesTests/TouchSelectionControllerClientAuraSiteIsolationTest.BasicSelectionIsolatedScrollMainframe/1 fails on all the platforms.

TBR=tdresser@chromium.org

Bug: 805017
Change-Id: I1ea7c82a4c8fc2fa8e83c83ac47ef65f98cd985f
Reviewed-on: https://chromium-review.googlesource.com/888753Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Commit-Queue: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532122}

content/browser/renderer_host/input/touch_selection_controller_client_aura_browsertest.cc

@@ -434,8 +434,9 @@ IN_PROC_BROWSER_TEST_P(TouchSelectionControllerClientAuraSiteIsolationTest,
   EXPECT_FALSE(ui::TouchSelectionMenuRunner::GetInstance()->IsRunning());
 }
 
+// https://crbug.com/805017
 IN_PROC_BROWSER_TEST_P(TouchSelectionControllerClientAuraSiteIsolationTest,
-                       BasicSelectionIsolatedScrollMainframe) {
+                       DISABLED_BasicSelectionIsolatedScrollMainframe) {
   GURL test_url(embedded_test_server()->GetURL(
       "a.com", "/cross_site_iframe_factory.html?a(a)"));
   EXPECT_TRUE(NavigateToURL(shell(), test_url));