Disable DumpAccessibilityTreeTest.AccessibilityTransition due to flakiness (Win/Mac)

content/browser/accessibility/dump_accessibility_tree_browsertest.cc

 // Copyright (c) 2012 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 <set>
 #include <string>
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/path_service.h"
@@ skipping 1138 matching lines @@
 }
 
 IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, AccessibilityTime) {
   RunHtmlTest(FILE_PATH_LITERAL("time.html"));
 }
 
 IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, AccessibilityTitle) {
   RunHtmlTest(FILE_PATH_LITERAL("title.html"));
 }
 
-IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, AccessibilityTransition) {
+#if defined(OS_WIN) || defined(OS_MACOSX)
+// Flaky on Win/Mac: crbug.com/508532
+#define MAYBE_AccessibilityTransition DISABLED_AccessibilityTransition
+#else
+#define MAYBE_AccessibilityTransition AccessibilityTransition
+#endif
+IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest,
+                       MAYBE_AccessibilityTransition) {
   RunHtmlTest(FILE_PATH_LITERAL("transition.html"));
 }
 
 IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, AccessibilityUl) {
   RunHtmlTest(FILE_PATH_LITERAL("ul.html"));
 }
 
 IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, AccessibilityVar) {
   RunHtmlTest(FILE_PATH_LITERAL("var.html"));
 }
 
 // crbug.com/281952
 IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, DISABLED_AccessibilityVideo) {
   RunHtmlTest(FILE_PATH_LITERAL("video.html"));
 }
 
 IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, AccessibilityWbr) {
   RunHtmlTest(FILE_PATH_LITERAL("wbr.html"));
 }
 
 }  // namespace content