Swarm all tests running on ClangToTLinux tester that were swarmed on at least one other bot already.

testing/buildbot/chromium.mac.json

 {
   "Mac GN": {
     "additional_compile_targets": [
       "gn_all"
     ],
     "gtest_tests": [
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "base_unittests"
       }
     ]
   },
   "Mac GN (dbg)": {
     "additional_compile_targets": [
       "accessibility_unittests",
       "base_unittests",
       "battor_agent",
       "cacheinvalidation_unittests",
@@ skipping 19 matching lines @@
       "printing_unittests",
       "remoting_all",
       "skia_unittests",
       "sql_unittests",
       "sync_unit_tests",
       "ui_base_unittests",
       "url_unittests"
     ],
     "gtest_tests": [
       {
+        "swarming": {
+          "can_use_on_swarming_builders": true
+        },
         "test": "base_unittests"
       }
     ]
   },
   "Mac10.10 Tests": {
     "gtest_tests": [
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
@@ skipping 1960 matching lines @@
       }
     ],
     "scripts": [
       {
         "name": "nacl_integration",
         "script": "nacl_integration.py"
       }
     ]
   }
 }