Add a ppapi_unittests_run target.

ppapi/ppapi_unittests.isolate

Index: ppapi/ppapi_unittests.isolate
diff --git a/tools/gn/gn_unittests.isolate b/ppapi/ppapi_unittests.isolate
similarity index 68%
copy from tools/gn/gn_unittests.isolate
copy to ppapi/ppapi_unittests.isolate
index cada5a0bad814f9359c5b2466d558e9ac053eed5..c77d6e5305325d8927d5f26f5d8468f21324391d 100644
--- a/tools/gn/gn_unittests.isolate
+++ b/ppapi/ppapi_unittests.isolate
@@ -6,15 +6,12 @@
     ['OS=="linux" or OS=="mac" or OS=="win"', {
       'variables': {
         'command': [
-          '<(PRODUCT_DIR)/gn_unittests<(EXECUTABLE_SUFFIX)',
-        ],
-        'files': [
-          'format_test_data/',
+          '<(PRODUCT_DIR)/ppapi_unittests<(EXECUTABLE_SUFFIX)',
         ],
       },
     }],
   ],
   'includes': [
-    '../../base/base.isolate',
+    '../base/base.isolate',
   ],
 }