Disable flaky WebViewPopupInteractiveTest.PopupPositioningMoved on Mac.

TBR=wjmaclean@chromium.org

Bug: 807446
Change-Id: Icc31a390ab51e2b0819c55cd6336df779ffda2c4
Reviewed-on: https://chromium-review.googlesource.com/894501Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533075}

chrome/browser/apps/guest_view/web_view_interactive_browsertest.cc

@@ -1316,7 +1316,8 @@ IN_PROC_BROWSER_TEST_F(WebViewPopupInteractiveTest, PopupPositioningBasic) {
 }
 
 // Flaky on ChromeOS and Linux: http://crbug.com/526886
-#if defined(OS_CHROMEOS) || defined(OS_LINUX)
+// TODO(crbug.com/807446): Flaky on Mac.
+#if defined(OS_CHROMEOS) || defined(OS_LINUX) || defined(OS_MACOSX)
 #define MAYBE_PopupPositioningMoved DISABLED_PopupPositioningMoved
 #else
 #define MAYBE_PopupPositioningMoved PopupPositioningMoved