Disable the flaky AccessibilityEventsIframeSrcChanged test

This test is highly flaky on Linux.

Bug: 1298770
Change-Id: I5ffc0de86cc9345eef2d71477337eb5ceaf05980
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3477175
Owners-Override: Martin Šrámek <msramek@chromium.org>
Auto-Submit: Martin Šrámek <msramek@chromium.org>
Reviewed-by: Sean Harrison <harrisonsean@chromium.org>
Commit-Queue: Martin Šrámek <msramek@chromium.org>
Cr-Commit-Position: refs/heads/main@{#973758}

content/browser/accessibility/dump_accessibility_events_browsertest.cc

@@ -661,8 +661,16 @@ IN_PROC_BROWSER_TEST_P(DumpAccessibilityEventsTest,
   RunEventTest(FILE_PATH_LITERAL("focus-listbox-multiselect.html"));
 }
 
+// TODO(crbug.com/1298770): Flaky on Linux.
+#if BUILDFLAG(IS_LINUX)
+#define MAYBE_AccessibilityEventsIframeSrcChanged \
+  DISABLED_AccessibilityEventsIframeSrcChanged
+#else
+#define MAYBE_AccessibilityEventsIframeSrcChanged \
+  AccessibilityEventsIframeSrcChanged
+#endif
 IN_PROC_BROWSER_TEST_P(DumpAccessibilityEventsTest,
-                       AccessibilityEventsIframeSrcChanged) {
+                       MAYBE_AccessibilityEventsIframeSrcChanged) {
   RunEventTest(FILE_PATH_LITERAL("iframe-src-changed.html"));
 }