Update isolate file for sync_integration_tests and enable swarming for it.

testing/buildbot/chromium_trybot.json

 {
   "compile_targets": [
     "all"
   ],
   "gtest_tests": [
     "accessibility_unittests",
     "app_list_unittests",
     {
       "test": "base_unittests",
       "swarming": {
@@ skipping 105 matching lines @@
     },
     {
       "test": "sbox_validation_tests",
       "platforms": ["win"]
     },
     {
       "test": "sbox_unittests",
       "platforms": ["win"]
     },
     "sql_unittests",
-    "sync_integration_tests",
+    {
+      "test": "sync_integration_tests",
+      "swarming": {
+        "can_use_on_swarming_builders": true,
+        "shards": 3
+      }
+    },
     "sync_unit_tests",
     "ui_unittests",
     {
       "test": "unit_tests",
       "swarming": {
         "can_use_on_swarming_builders": true,
         "shards": 2
       }
     },
     "url_unittests",
@@ skipping 63 matching lines @@
     "tools/perf/.*",
     "tools/telemetry/.*",
     "tools/whitespace.txt"
   ],
 
   "filter_builders": [
     "linux_chromium_clang_dbg",
     "mac_chromium_rel"
   ]
 }