Converted accessibility_unittests to run on Swarming everywhere.

testing/buildbot/chromium.memory.fyi.json

 {
   "Linux ChromeOS MSan Tests": {
     "gtest_tests": [
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "accessibility_unittests"
       },
       {
         "test": "app_list_unittests"
       },
       {
         "test": "aura_unittests"
       },
       {
         "test": "base_unittests"
@@ skipping 139 matching lines @@
         "test": "views_unittests"
       },
       {
         "test": "wm_unittests"
       }
     ]
   },
   "Linux MSan Tests": {
     "gtest_tests": [
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "accessibility_unittests"
       },
       {
         "test": "app_list_unittests"
       },
       {
         "test": "aura_unittests"
       },
       {
         "test": "base_unittests"
@@ skipping 147 matching lines @@
   },
   "Linux TSan Tests": {
     "disabled_tests": {
       "app_shell_browsertests": "http://crbug.com/455633",
       "browser_tests": "Too many errors, clean content_browsertests first. http://crbug.com/368525",
       "cc_unittests": "http://crbug.com/437454",
       "interactive_ui_tests": "http://crbug.com/455679"
     },
     "gtest_tests": [
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "accessibility_unittests"
       },
       {
         "test": "app_list_unittests"
       },
       {
         "test": "aura_unittests"
       },
       {
         "swarming": {
@@ skipping 116 matching lines @@
       },
       {
         "test": "views_unittests"
       },
       {
         "test": "wm_unittests"
       }
     ]
   }
 }