Disable the AccessibilityDl test due to failures on bot.

NOTRY=true
BUG=418600

Review URL: https://codereview.chromium.org/613693003

Cr-Commit-Position: refs/heads/master@{#297186}

content/browser/accessibility/dump_accessibility_tree_browsertest.cc

@@ -523,7 +523,8 @@ IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, AccessibilityDiv) {
   RunTest(FILE_PATH_LITERAL("div.html"));
 }
 
-IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, AccessibilityDl) {
+// crbug.com/418600
+IN_PROC_BROWSER_TEST_F(DumpAccessibilityTreeTest, DISABLED_AccessibilityDl) {
   RunTest(FILE_PATH_LITERAL("dl.html"));
 }