android: Add entry for 'skia_unittests' to UNIT_TESTS list.

scripts/slave/recipes/android/tester.expected/no_provision_devices_when_no_tests.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "tryserver.chromium.linux",
       "--builder",
       "android_dbg_tests_recipe",
@@ skipping 122 matching lines @@
     "cwd": "[SLAVE_BUILD]/src",
     "name": "git diff to analyze patch",
     "stdout": "/path/to/tmp/"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/build/gyp_chromium",
       "--analyzer",
-      "{\"files\": [\"foo.cc\"], \"targets\": [\"android_webview_test_apk\", \"chrome_shell_test_apk\", \"content_shell_test_apk\", \"chrome_sync_shell_test_apk\", \"android_webview_unittests\", \"base_unittests\", \"breakpad_unittests\", \"cc_unittests\", \"components_unittests\", \"content_browsertests\", \"content_unittests\", \"events_unittests\", \"gl_tests\", \"gpu_unittests\", \"ipc_tests\", \"media_unittests\", \"net_unittests\", \"sandbox_linux_unittests\", \"sql_unittests\", \"sync_unit_tests\", \"ui_android_unittests\", \"ui_base_unittests\", \"ui_touch_selection_unittests\", \"unit_tests\", \"junit_unit_tests\"]}",
+      "{\"files\": [\"foo.cc\"], \"targets\": [\"android_webview_test_apk\", \"chrome_shell_test_apk\", \"content_shell_test_apk\", \"chrome_sync_shell_test_apk\", \"android_webview_unittests\", \"base_unittests\", \"breakpad_unittests\", \"cc_unittests\", \"components_unittests\", \"content_browsertests\", \"content_unittests\", \"events_unittests\", \"gl_tests\", \"gpu_unittests\", \"ipc_tests\", \"media_unittests\", \"net_unittests\", \"sandbox_linux_unittests\", \"skia_unittests\", \"sql_unittests\", \"sync_unit_tests\", \"ui_android_unittests\", \"ui_base_unittests\", \"ui_touch_selection_unittests\", \"unit_tests\", \"junit_unit_tests\"]}",
       "/path/to/tmp/json"
     ],
     "env": {
       "GYP_CROSSCOMPILE": "1",
       "GYP_DEFINES": "OS=android component=static_library fastbuild=1 gomadir='[BUILD]/goma' target_arch=arm use_goma=1"
     },
     "name": "analyze",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"build_targets\": [@@@",
@@ skipping 30 matching lines @@
       "--goma-dir",
       "[BUILD]/goma",
       "--",
       "content_browsertests"
     ],
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "compile"
   }
-]
+]