Re-enable some previously flaky single_process_mash_browser_tests

Tests were blacklisted because of flakiness due to crbug.com/884589.  Now that it's fixed, renable these tests.

Bug: 884589
Change-Id: Idc1b073c7a50636778231177488112f778d649b5
Reviewed-on: https://chromium-review.googlesource.com/1246954Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Ryan Cui <rcui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594499}

testing/buildbot/filters/chromeos.single_process_mash.browser_tests.filter

@@ -172,18 +172,6 @@
 # Default extension tests.
 -DefaultProfileExtensionBrowserTest.NoExtensionHosts
 
-# Encrypted media tests are flaky due to race condition. crbug.com/880584
--ECKEncryptedMediaTest.*
--EncryptedMediaTest.*
--CDM_9/ECKEncryptedMediaTest.*
--CDM_10/ECKEncryptedMediaTest.*
--CDM_11/ECKEncryptedMediaTest.*
--MSE_ClearKey/EncryptedMediaTest.*
--MSE_ExternalClearKey/EncryptedMediaTest.*
--MSE_Widevine/EncryptedMediaTest.*
--SRC_ClearKey/EncryptedMediaTest.*
--SRC_ExternalClearKey/EncryptedMediaTest.*
-
 # Failing on ASAN bot. crbug.com/882631
 -ExtensionWebRequestApiTest.WebRequestTypes
 
@@ -204,12 +192,6 @@
 -ManagedWithoutPermission/ManagedWithoutPermissionPlatformKeysTest.*
 -ManagedWithPermission/ManagedWithPermissionPlatformKeysTest.*
 
-# Needs video surface layer support. Should be fixed when renderers don't use
-# the window service for embedding.
-# https://crbug.com/884589 https://crbug.com/881574
--MediaEngagementBrowserTest.*
--MediaEngagementAutoplayBrowserTest.*
-
 # Flaky https://crbug.com/887175
 -PrerenderBrowserTest.PrerenderHTML5VideoJs