Disable Flaky tests on vulkan_content_browsertests

A series of tests have been flaking often on vulkan_content_browsertests. These
were also flaking on non-vulkan configurations as well, but the flake rate was
negatively impacting the ability for GPU Pixel Wranglers to identify actual
GPU failures.

These tests were not demonstrating any GPU specific failures, so we will disable
them until their base flakiness can be addressed.

TBR=penghuang@chromium.org
TEST = vulkan_content_browsertests
   All/DumpAccessibilityTreeTest.Accessibility*
   All/ScrollBehaviorBrowserTest.OverflowScrollInterruptedByWheelScroll/1

Bug: 1134297
Change-Id: Ib302e29dfd0802cbcb450abf6501c4622fb25d73
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2460985Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815279}

testing/buildbot/filters/gpu.skiarenderer_vulkan_content_browsertests.filter

 # TODO(jonross): Remove once Finch completes.
 
 # Consistent Timeout. https://crbug.com/1116577
--BackForwardCacheBrowserTest.ReplacedNavigationEntry
+-BackForwardCacheBrowserTest.ReplacedNavigationEntry
\ No newline at end of file
+
+# Highly Flaky, even without Vulkan https://crbug.com/1134297
+-All/DumpAccessibilityTreeTest.Accessibility*
+-All/ScrollBehaviorBrowserTest.OverflowScrollInterruptedByWheelScroll/1