Turn mini_installer_tests on by default on Win10.

This makes mini_installer_tests non-experimental and adds them
to the CQ on win10_chromium_x64_rel_ng.

R=grt@chromium.org, mmeade@chromium.org, sergeyberezin@chromium.org
BUG=827546

Change-Id: I742d7003dd706949ee73e8e4febaa91b52a52bf8
Reviewed-on: https://chromium-review.googlesource.com/1013269Reviewed-by: Sergey Berezin <sergeyberezin@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551755}

testing/buildbot/chromium.win.json

@@ -1141,11 +1141,15 @@
     ],
     "isolated_scripts": [
       {
-        "experiment_percentage": 10,
         "isolate_name": "mini_installer_tests",
         "name": "mini_installer_tests",
         "swarming": {
-          "can_use_on_swarming_builders": true
+          "can_use_on_swarming_builders": true,
+          "dimension_sets": [
+            {
+              "integrity": "high"
+            }
+          ]
         }
       }
     ]

testing/buildbot/test_suites.pyl

@@ -1817,7 +1817,13 @@
 
   'win_specific_isolated_scripts': {
     'mini_installer_tests': {
-      'experiment_percentage': 10,
+      'swarming': {
+        'dimension_sets': [
+          {
+            'integrity': 'high',
+          }
+        ],
+      },
     },
   },