Disable WebViewTest.Shim_TestNestedSubframes on Mac.

chrome/browser/apps/guest_view/web_view_browsertest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <queue>
 #include <set>
 #include <utility>
 
 #include "base/callback_helpers.h"
 #include "base/files/file_util.h"
@@ skipping 1463 matching lines @@
 
 IN_PROC_BROWSER_TEST_P(WebViewTest, Shim_TestNavigateAfterResize) {
   TestHelper("testNavigateAfterResize", "web_view/shim", NO_TEST_SERVER);
 }
 
 IN_PROC_BROWSER_TEST_P(WebViewTest, Shim_TestNestedCrossOriginSubframes) {
   TestHelper("testNestedCrossOriginSubframes",
              "web_view/shim", NEEDS_TEST_SERVER);
 }
 
-IN_PROC_BROWSER_TEST_P(WebViewTest, Shim_TestNestedSubframes) {
+#if defined(OS_MACOSX)
+// Flaky on Mac. See https://crbug.com/674904.
+#define MAYBE_Shim_TestNestedSubframes DISABLED_Shim_TestNestedSubframes
+#else
+#define MAYBE_Shim_TestNestedSubframes Shim_TestNestedSubframes
+#endif
+IN_PROC_BROWSER_TEST_P(WebViewTest, MAYBE_Shim_TestNestedSubframes) {
   TestHelper("testNestedSubframes", "web_view/shim", NO_TEST_SERVER);
 }
 
 IN_PROC_BROWSER_TEST_P(WebViewTest, Shim_TestRemoveSrcAttribute) {
   TestHelper("testRemoveSrcAttribute", "web_view/shim", NO_TEST_SERVER);
 }
 
 IN_PROC_BROWSER_TEST_P(WebViewTest, Shim_TestReassignSrcAttribute) {
   TestHelper("testReassignSrcAttribute", "web_view/shim", NO_TEST_SERVER);
 }
@@ skipping 2414 matching lines @@
                        ClosingChromeSignInShouldNotCrash) {
   GURL signin_url{"chrome://chrome-signin"};
 
   AddTabAtIndex(0, signin_url, ui::PAGE_TRANSITION_TYPED);
   AddTabAtIndex(1, signin_url, ui::PAGE_TRANSITION_TYPED);
   WaitForWebViewInDom();
 
   chrome::CloseTab(browser());
 }
 #endif