gpu: Suppress encrypted video content_browsertests on vulkan

TBR=backer@chromium.org

Bug: 1164594
Change-Id: I3530e32cf5d9fb1d7aa7d9ad972a4bf306f60a2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2618907Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>
Auto-Submit: Sunny Sachanandani <sunnyps@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841766}

testing/buildbot/filters/gpu.skiarenderer_vulkan_content_browsertests.filter

@@ -6,3 +6,8 @@
 # Highly Flaky, even without Vulkan https://crbug.com/1134297
 -All/DumpAccessibilityTreeTest.Accessibility*
 -All/ScrollBehaviorBrowserTest.OverflowScrollInterruptedByWheelScroll/1
+
+# Consistent failures.  https://crbug.com/1164594
+-SRC_ExternalClearKey/EncryptedMediaTest.Playback_VideoOnly_WebM_AV1_10bit/0
+-MSE_ExternalClearKey/EncryptedMediaTest.Playback_VideoOnly_WebM_AV1_10bit/0
+-MSE_ExternalClearKey/EncryptedMediaTest.Playback_VideoOnly_MP4_AV1_10bit/0
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