Enable interactive_ui_tests on Win10 Tests x64 (dbg).

I can't repro the failures anywhere outside of the real environment.

BUG=818832
R=martiniss@chromium.org

Change-Id: I9ccaa3bf5f7e357f879c4d804310d34b0e1abaaa
Reviewed-on: https://chromium-review.googlesource.com/1070192Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Commit-Queue: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561417}

testing/buildbot/chromium.win.json

@@ -1448,6 +1448,13 @@
         },
         "test": "installer_util_unittests"
       },
+      {
+        "swarming": {
+          "can_use_on_swarming_builders": true,
+          "shards": 2
+        },
+        "test": "interactive_ui_tests"
+      },
       {
         "swarming": {
           "can_use_on_swarming_builders": true

testing/buildbot/test_suite_exceptions.pyl

@@ -1493,8 +1493,6 @@
       'Chromium Win 10 GCE Tests',
       # chromium.memory
       'Linux TSan Tests',
-      # chromium.win
-      'Win10 Tests x64 (dbg)',
     ],
     'modifications': {
       # chromium.clang